Development of a framework for truss-braced wing conceptual MDO

The paper describes the development of a multidisciplinary design optimization framework for conceptual design of truss-braced wing configurations. This unconventional configuration requires specialized analysis tools supported by a modular and flexible framework to accommodate different configurations. While the previous framework developed at Virginia Tech was a monolithic Fortran-77 code, the need for more flexibility for complex truss-braced wing configurations was addressed by the development of this new framework, which is based on Phoenix Integration ModelCenter^TM environment. The framework uses updated structural and aerodynamic design modules that enable a more general geometry definition. The new framework, thus, provides a foundation for future design concepts, especially multi-member truss-braced wing configurations. The fuel saving potential of these truss-braced wing configurations is presented by comparing different truss designs with gradually increased level of complexity.     

Labeling Schemes for Dynamic Tree Networks

Distance labeling schemes are composed of a marker algorithm for labeling the vertices of a graph with short labels, coupled with a decoder algorithm allowing one to compute the distance between any two vertices directly from their labels (without using any additional information). As applications for distance labeling schemes concern mainly large and dynamically changing networks, it is of interest to study distributed dynamic labeling schemes. The current paper considers the problem on dynamic trees, and proposes efficient distributed schemes for it. The paper first presents a labeling scheme for distances in the dynamic tree model, with amortized message complexity O(log² n) per operation, where n is the size of the tree at the time the operation takes place. The protocol maintains O(log² n) bit labels. This label size is known to be optimal even in the static scenario. A more general labeling scheme is then introduced for the dynamic tree model, based on extending an existing static tree labeling scheme to the dynamic setting. The approach fits a number of natural tree functions, such as distance, separation level, and flow. The main resulting scheme incurs an overhead of an O(log n) multiplicative factor in both the label size and amortized message complexity in the case of dynamically growing trees (with no vertex deletions). If an upper bound on n is known in advance, this method yields a different tradeoff, with an O(log² n/log log n) multiplicative overhead on the label size but only an O(log n/log log n) overhead on the amortized message complexity. In the fully dynamic model the scheme also incurs an increased additive overhead in amortized communication, of O(log² n) messages per operation.     

Perceived density of road maps

Maps should be designed so that users can comprehend and use the information. Display decisions, such as choosing the scale at which an area is shown, depend on properties of the displayed information such as the perceived density (PD) of the information. Taking a psychophysical approach we suggest that the PD of information in a road map is related to the scale and properties of the mapped area. 54 participants rated the PD of 60 maps from different regions. We provide a simple model that predicts the PD of electronic road map displays, using the logarithm of the number of roads, the logarithm of the number of junctions and the length of the shown roads. The PD model was cross-validated using a different set of 60 maps (n = 44). The model can be used for automatically adjusting display scales and for evaluating map designs, considering the required PD to perform a map-related task.     

A transfer matrix model of large deformations of curved rods

Transfer matrix models have been frequently used to analyze the structural behavior of rods, including curved and pretwisted ones. The advantages of these models include their relative simplicity, numerical efficiency and ease of implementation. Previous investigations did not include nonlinear analyses of curved rods that undergo large deformations. The present paper describes a nonlinear transfer matrix model of curved and pretwisted rods, which is capable of analyzing very large spatial deformations. The rod is divided into segments. A body system of coordinates is attached to each segment. This system translates and rotates with the segment during the deformation. If the segments are kept small enough, the local deformations of each segment, relative to its body system of coordinates, are small. The segments’ systems of coordinates rotate relative to their neighbors and if this rotation is dealt with properly, large rotations and displacement of the curved rod can be analyzed. In spite of its nonlinear nature, the model remains relatively simple and efficient. The new model is used to solve a few problems and the results show very good agreement with other analytical, finite-element, and experimental results.     

Highly Efficient Ge-Rich Ge<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>Pb<Subscript>1−<Emphasis Type="Italic">x</Emphasis></Subscript>Te Thermoelectric Alloys

The search for alternative energy sources is presently at the forefront of applied research. In this context, thermoelectricity for direct energy conversion from thermal to electrical energy plays an important role. This paper is concerned with the development of highly efficient p-type Ge _x Pb_1−x Te alloys for thermoelectric applications, using spark plasma sintering. The carrier concentration of GeTe was varied by alloying of PbTe and/or by Bi₂Te₃ doping. Very high ZT values up to ~1.8 at 500°C were obtained by doping Pb_0.13Ge_0.87Te with 3 mol% Bi₂Te₃.     

Watermarks encrypted in a concealogram and deciphered by a modified joint-transform correlator

We describe an electro-optical method of deciphering a watermark from a recently invented encoded image termed a concealogram. The watermark is revealed as a result of spatial correlation between two concealograms, one containing the watermark and the other containing the deciphering key. The two are placed side by side on the input plane of a modified joint-transform correlator. When the input plane is illuminated by a plane wave, the watermark image is reconstructed on part of the correlator's output plane. The key function deciphers the concealed watermark from the visible picture only when the two specific concealograms are matched. To illustrate the system's performance, both simulation and experimental results are presented.     

Significant Enhancement of Proton Transport in Bioinspired Peptide Fibrils by Single Acidic or Basic Amino Acid Mutation

Bioinspired materials are extremely suitable for the development of biocompatible and environmentally friendly functional materials. Peptide‐based assemblies are remarkably attractive for such tasks, since they provide a simple way to fuse together functional and structural protein motifs in artificial materials. Motivated by this idea, it is shown here that the introduction of a single acidic, or basic, amino acid into the side chain of a heptameric self‐assembling peptide increases proton conduction in the resulting fibers by two orders of magnitude. This self‐doping effect is much more pronounced than the effect induced by the peptide's acidic and basic termini groups. Furthermore, the self‐doping process is found to be significantly more effective for acidic side chains than for basic ones due to both much more effective self‐doping process, resulting in an order of magnitude larger concentration of charge carriers for the acidic assemblies, and higher mobility of the formed charge carriers – almost threefolds in this case. This work facilitates the realization of unique bioinspired self‐assembled proton conducting materials that may find uses in the emerging bioprotonic technology. The presented design flexibility and, in particular, the ability to introduce both proton and proton holes further extend the usefulness of these materials.     

Development of a sweet pepper harvesting robot

This paper presents the development, testing and validation of SWEEPER, a robot for harvesting sweet pepper fruit in greenhouses. The robotic system includes a six degrees of freedom industrial arm equipped with a specially designed end effector, RGB‐D camera, high‐end computer with graphics processing unit, programmable logic controllers, other electronic equipment, and a small container to store harvested fruit. All is mounted on a cart that autonomously drives on pipe rails and concrete floor in the end‐user environment. The overall operation of the harvesting robot is described along with details of the algorithms for fruit detection and localization, grasp pose estimation, and motion control. The main contributions of this paper are the integrated system design and its validation and extensive field testing in a commercial greenhouse for different varieties and growing conditions. A total of 262 fruits were involved in a 4‐week long testing period. The average cycle time to harvest a fruit was 24 s. Logistics took approximately 50% of this time (7.8 s for discharge of fruit and 4.7 s for platform movements). Laboratory experiments have proven that the cycle time can be reduced to 15 s by running the robot manipulator at a higher speed. The harvest success rates were 61% for the best fit crop conditions and 18% in current crop conditions. This reveals the importance of finding the best fit crop conditions and crop varieties for successful robotic harvesting. The SWEEPER robot is the first sweet pepper harvesting robot to demonstrate this kind of performance in a commercial greenhouse.