Recent studies in wave energy have highlighted the need for a structured innovation approach in wave energy converter (WEC) design because cost-of-energy estimates have remained high. One specific ...innovation being investigated by the National Renewable Energy Laboratory is WEC geometry control, which uses control surfaces in combination with an oscillating surge WEC (OSWEC) to increase device availability and power generation while limiting structural costs. This study performs the first analysis of annual performance for a novel OSWEC with geometry control to understand how the geometry control affects availability, annual power generation, and structural loadings like the power-take-off (PTO) torque or surge foundation force. Device hydrodynamic coefficients are calculated using linear potential theory for six geometry configurations. A nonideal PTO system is assumed and quadratic viscous damping losses are considered. Annual performance is evaluated and compared for three U.S. wave energy sites. The WEC geometry and PTO system are controlled on a sea-state basis to optimize for power capture while remaining under limits set on motion amplitude and structural loads. Results indicate that geometry control can increase availability up to 25 days in an average year depending on design limits, increase average power generation, and significantly reduce peak structural loads.
A dry-lab test rig is a powerful means to reduce costs in the design process of a wave energy conversion system (WECs). A dry-lab test rig technique allows the use of real components inside a ...simulation of a mathematical model. This paper presents the development of an innovative dry-lab test rig for the mechanicalhydraulic power take-off (MHPTO) unit of WECs. The development of a drylab test rig of MHPTO involves several processes, such as three-dimension (3D) modelling, component purchasing, structure fabrication, component installation, and operational testing. The developed dry-lab test rig consists of two main parts, such as the simulated wave emulator plant and the real MHPTO unit plant. The simulated wave emulator plant was developed in this test rig to replicate the interaction motion between the ocean wave motion and the wave absorber device. The developed dry-lab test rig was tested using five different irregular wave input conditions to ensure it could perform under the five different wave input conditions. The overall results demonstrate that the developed dry-lab test rig was successfully performed in all sea states. From the results, the profile of electrical power produced by the real MHPTO unit can be clearly obtained in each sea state.
The critical advantage of passive microwave imaging is that it can be used in all-day and in low visibility conditions, such as hazes, fogs, clouds, smokes, and sandstorms. In this article, the ...ground-based passive interferometric microwave sensor (PIMS) is proposed to detect civil aircrafts, especially in low visibility conditions. The fundamental of civil aircraft detection by a ground-based PIMS is introduced and analyzed. Numerical simulations are performed to assess its feasibility and detection performance, and the impact of the low visibility weather is analyzed and discussed. To verify the practicability of civil aircraft detection by the ground-based PIMS, a series of experiments have been performed by a ground-based X-band PIMS, and a data processing procedure is introduced, which contains a target detection algorithm. Experimental results have demonstrated that the civil aircrafts can be accurately detected and consecutively tracked by the ground-based PIMS using the target detection algorithm. Meanwhile, a mirrored TB phenomenon, the TB change, and an application scheme are analyzed and discussed. As a conclusion, the ground-based PIMS can be considered as a powerful complementary tool for civil aircraft detection.
Gaeumannomyces graminis var. graminis (Ggg) has been the etiological agent of take-all root rot (TARR) in St. Augustinegrass (Stenotaphrum secundatum) and root decline of the other warm-season ...turfgrasses. Seventy-five Ggg isolates were obtained from St. Augustinegrass in central and east Texas. Evaluation of colony morphologies on potato dextrose agar (PDA) within 2 wk and follow-up multilocus phylogenic analyses revealed three phenotypic groups associated with different Gaeumannomyces species: (i) G. floridanus, highly melanized with round colony formation; (ii) G. arxii, none to slightly melanized with round colony formation; and (iii) G. graminicola, highly melanized with irregular colony formation. Further examination with representative isolates from each group revealed that their phenotypic characterizations supported the distinctive genetic groups within Ggg associated with St. Augustinegrass TARR. Gaeumannomyces floridanus isolates grew faster at warmer temperature (30 C) than G. arxii or G. graminicola. Pathogenicity assays using rice seedlings indicated that G. floridanus was more aggressive in disease symptom development than G. arxii or G. graminicola. A multilocus phylogeny reconstruction supported that most of Gaeumannomyces isolates tested in this study were separated into three phylogenetically distinct groups: G. floridanus, G. arxii, and G. graminicola. The resolution of intravarietal complexities of causal fungi of TARR is important for proper diagnostics and management strategies for TARR in St. Augustinegrass and other root-decline diseases in warm-season turfgrasses.
The article explores the association between within-household couples’ parental leave take-up strategies and parents’ earning capacity (hourly wages) and their workplace characteristics. The results, ...based on the social security register data from Luxembourg, reveal that a couple strategy where both partners take parental leave is more likely when the partners have equal earning capacity, when the mother works in the sector of education, health and social services rather than in other sectors, and when the father is employed in a larger-sized company. Couples where the mother earns more than the father are more likely to opt for a strategy where neither parent takes any leave. The economic sector moderates the effect of fathers’ wages on the probability of choosing the strategy where both partners take leave.
Airborne applications demand exceptional overall radar system performance and eminently high output power for high range target detection. The frequency modulated continuous wave (FMCW) radar system ...presented in this article is capable of achieving this task due to its high output power at 94-GHz center frequency with over 26-GHz tuning range. Nevertheless, the radar still provides a small form factor and low power consumption of 4.25 W at 5 V single Universal Serial Bus (USB) supply. The key system component is a Silicon Germanium (SiGe) bipolar complementary metal-oxide-semiconductor (BiCMOS) monolithic microwave integrated circuit (MMIC) that contains a 94-GHz voltage-controlled oscillator (VCO), and a 27-GHz VCO for dual-loop phase-locked loop (PLL) stabilization, a power amplifier (PA), and two receive mixers. It generates frequency ramps between 83- and 109-GHz with a maximum output power of 19.7 dBm at its output after the bond wires on the printed circuit board (PCB) and 14.8-dBm output power at the radar's transmit (TX)-waveguide WR-10-flange. The sensor was also tested in a temperature range from -40 °C to +70 °C with menial deviation. Thus, the system offers high system dynamic range and far distance target detection range. Following a detailed system description, we finally present the FMCW range and Doppler measurements performed with the presented radar sensor as well as the application on unmanned aerial vehicles (UAVs) for flight altitude control and as airborne collision avoidance system (ACAS).
Perceptual decisions rely on accumulating sensory evidence. This computation has been studied using either drift diffusion models or neurobiological network models exhibiting winner-take-all ...attractor dynamics. Although both models can account for a large amount of data, it remains unclear whether their dynamics are qualitatively equivalent. Here we show that in the attractor model, but not in the drift diffusion model, an increase in the stimulus fluctuations or the stimulus duration promotes transitions between decision states. The increase in the number of transitions leads to a crossover between weighting mostly early evidence (primacy) to weighting late evidence (recency), a prediction we validate with psychophysical data. Between these two limiting cases, we found a novel flexible categorization regime, in which fluctuations can reverse initially-incorrect categorizations. This reversal asymmetry results in a non-monotonic psychometric curve, a distinctive feature of the attractor model. Our findings point to correcting decision reversals as an important feature of perceptual decision making.
To enhance the take–over performance by human drivers of Level–2 automated vehicles (AV), we developed a design concept that presents the AV's planned trajectory as augmented reality in the ...windshield. We hypothesized that, even when the AV does not release a take–over request before a potential crash (i.e., silent failure), the planned trajectory would allow the driver to foresee the crash and enhance the take–over performance. To test this hypothesis, we conducted a driving–simulator experiment where participants monitored the driving status of an AV with or without the planned trajectory in the context of silent failures. The results showed that, when the planned trajectory was projected in the windshield as if it were an augmented–reality display, the crash rate decreased by 10% and the take–over response time decreased by 825 ms compared to when the planned trajectory was not provided.
•Projecting the planned trajectory of an automated vehicle (AV) in the windshield as augmented reality.•Enhancing the take–over performance even when the Level–2 AV does not release an explicit take–over request.•High perceived usefulness and satisfaction toward the planned trajectory.
Fully autonomous vehicles, capable of completing entire end-to-end journeys without the interference of a human driver, will be one of the biggest transforming technologies of the next decades. As ...the journey towards fully autonomous vehicles progresses, there will be an increase in the number of highly automated vehicles on the roads, requiring the human driver to take back control in situations, which cannot be handled by the vehicle autonomously. These human-robot take-over requests can lead to safety risks, in particular in scenarios when the driver fails to understand the take-over request and, hence, lacks situational awareness. This paper presents the acceptance and usability assessment of a haptic feedback driver seat capable of informing the driver of a take-over request through static mechano-tactile haptic feedback. The seat is equipped with an embedded array of soft pneumatic actuators, that have been fully modelled and characterised. The evaluation process of the haptic feedback seat engaged 21 participants who experienced both auditory and haptic feedback from the seat in a number of simulation experiments within a driving simulator. The vehicular technology was assessed through well-established methods to understand the acceptance (usefulness and satisfaction) and usability of the haptic feedback driver seat.
As human-machine collaborative driving systems, highly automated driving vehicles require human drivers to take over when take-over requests are triggered. Extensive studies have shown that drivers' ...take-over performance is affected by their fatigue state, traffic conditions, and the take-over time budget (TB). However, there is still a paucity of a systematic understanding of how these factors affect take-over performance, which prevents the implementation of adaptive take-over systems. This study establishes a highly accurate take-over performance prediction model to systematically explore the effects of these factors on take-over performance and to propose an adaptive TB adjustment strategy for highly automated driving vehicles. First, we propose metrics to evaluate drivers' fatigue states and the relative positions of surrounding traffic. Second, a generalized additive model is established to predict take-over performance and accurately evaluate the influence of the aforementioned factors on take-over performance. Based on the model, we propose an adaptive adjustment strategy of the TB for take-over systems and demonstrate its effectiveness by a verification experiment. This study contributes to understanding the influence of drivers' passive fatigue states, the relative positions of surrounding traffic, and the TB on drivers' take-over performance as well as to the development of adaptive take-over systems for highly automated vehicles.
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