Wave propagation is observed through a negative permeability metamaterial immersed in gaseous plasma. A 3D array of split ring resonators (SRR) is enveloped by an inductively heated argon plasma with ...a nominal plasma frequency of 2.65 GHz. Transmission spectra show electromagnetic waves traverse the composite medium from 1.3-1.7 GHz for which the permeability of the SRRs and the permittivity of the plasma are simultaneously negative. Only surface waves and evanescence are observed outside this frequency band. The edge of the transmission band also shows negative group velocity, albeit with high wave attenuation. The free electron density of the plasma is coupled to the inductive heating, allowing dynamic reconfiguration of the metamaterial's frequency band and wave impedance.
Despite high potentials of power-split hybrid electric vehicles (PS-HEV), their design and control problems are nontrivial. For instance, there exist 24 ways of connecting four components (two ...electric machines, an engine, and a vehicle wheel) with a planetary gear (PG), and more than thousand ways with two PGs. Furthermore, when PG and final drive ratios are considered design variables, finding an optimal design that fulfills both high fuel economy and short acceleration time is a challenge. In this paper, a systematic configuration searching methodology is proposed to find an optimal single PG PS-HEV configuration for both performance metrics. First, by identifying all the possible single PG configurations and reorganizing them into a compound lever design space, the performance metrics are explored in the continuous design space. Then, the designs are mapped onto the "fuel economy - acceleration performance" plane to solve the multiobjective configuration selection problem. Thus, a highly promising configuration ("o6"), which outperforms Prius design in the acceleration performance, is selected among Pareto Frontier. A case study has been conducted on a sport utility vehicle specification. The study illustrates that the performance metrics of candidate configurations change significantly, and thus, selecting a proper configuration is crucial to evoke full potential of the given powertrain components.
In concrete structures, surface cracks are important indicators of structural durability and serviceability. Generally, concrete cracks are visually monitored by inspectors who record crack ...information such as the existence, location, and width. Manual visual inspection is often considered ineffective in terms of cost, safety, assessment accuracy, and reliability. Digital image processing has been introduced to more accurately obtain crack information from images. A critical challenge is to automatically identify cracks from an image containing actual cracks and crack-like noise patterns (e.g. dark shadows, stains, lumps, and holes), which are often seen in concrete structures. This article presents a methodology for identifying concrete cracks using machine learning. The method helps in determining the existence and location of cracks from surface images. The proposed approach is particularly designed for classifying cracks and noncrack noise patterns that are otherwise difficult to distinguish using existing image processing algorithms. In the training stage of the proposed approach, image binarization is used to extract crack candidate regions; subsequently, classification models are constructed based on speeded-up robust features and convolutional neural network. The obtained crack identification methods are quantitatively and qualitatively compared using new concrete surface images containing cracks and noncracks.
Unified virtual memory was introduced in modern GPUs to enable a new programming model for programmers. This method manages memory pages between the GPU and CPU automatically, reducing the complexity ...of data management for programmers. However, when a GPU programs generates a large memory footprint that exceeds the GPU memory capacity, thrashing can occur, leading to significant performance degradation. To address this issue, this paper proposes a thread throttling that restricts the active thread groups, thereby alleviating memory oversubscription and improving performance. The proposed method adjusts the active thread group at compile time to ensure that their memory footprints fit within the available memory capacity. The effectiveness of the proposed method was evaluated using GPU programs that experience memory oversubscription. The results showed that our approach improved the performance of the original programs by 3.44
×
on average. This represents a 1.53
×
performance improvement compared to static thread throttling.
We propose a new volume reconstruction technique based on the six-direction cubic box-spline M6. M6 is C1 continuous and possesses an approximation order of three, the same as that of the ...tri-quadratic B-spline but with much lower degree. In fact, M6 has the lowest degree among the symmetric box-splines on Z3 with at least C1 continuity. We analyze the polynomial structure induced by the shifts of M6 and propose an efficient analytic evaluation algorithm for splines and their derivatives (gradient and Hessian) based on the high symmetry of M6. To verify the evaluation algorithm, we implement a real-time GPU (graphics processing unit) isosurface raycaster which exhibits interactive performance (54.5 fps (frames per second) with 2413 dataset on 5122 framebuffer) on a modern graphics hardware. Moreover, we analyze M6 as a reconstruction filter and state that it is comparable to the tri-cubic B-spline, which possesses a higher approximation order.
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Over the past decade, conductive hydrogels have received great attention as tissue-interfacing electrodes due to their soft and tissue-like mechanical properties. However, a trade-off between robust ...tissue-like mechanical properties and good electrical properties has prevented the fabrication of a tough, highly conductive hydrogel and limited its use in bioelectronics. Here, we report a synthetic method for the realization of highly conductive and mechanically tough hydrogels with tissue-like modulus. We employed a template-directed assembly method, enabling the arrangement of a disorder-free, highly-conductive nanofibrous conductive network inside a highly stretchable, hydrated network. The resultant hydrogel exhibits ideal electrical and mechanical properties as a tissue-interfacing material. Furthermore, it can provide tough adhesion (800 J/m
) with diverse dynamic wet tissue after chemical activation. This hydrogel enables suture-free and adhesive-free, high-performance hydrogel bioelectronics. We successfully demonstrated ultra-low voltage neuromodulation and high-quality epicardial electrocardiogram (ECG) signal recording based on in vivo animal models. This template-directed assembly method provides a platform for hydrogel interfaces for various bioelectronic applications.
Crack assessment is an essential process in the maintenance of concrete structures. In general, concrete cracks are inspected by manual visual observation of the surface, which is intrinsically ...subjective as it depends on the experience of inspectors. Further, it is time-consuming, expensive, and often unsafe when inaccessible structural members are to be assessed. Unmanned aerial vehicle (UAV) technologies combined with digital image processing have recently been applied to crack assessment to overcome the drawbacks of manual visual inspection. However, identification of crack information in terms of width and length has not been fully explored in the UAV-based applications, because of the absence of distance measurement and tailored image processing. This paper presents a crack identification strategy that combines hybrid image processing with UAV technology. Equipped with a camera, an ultrasonic displacement sensor, and a WiFi module, the system provides the image of cracks and the associated working distance from a target structure on demand. The obtained information is subsequently processed by hybrid image binarization to estimate the crack width accurately while minimizing the loss of the crack length information. The proposed system has shown to successfully measure cracks thicker than 0.1 mm with the maximum length estimation error of 7.3%.
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