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A new method to visualize the coupling path is proposed to help solve electromagnetic compatibility problems. By using the reciprocity theorem and the concept of reaction, the coupling density coefficient (CC) is defined. Integration of the CC on closed surfaces equals the coupled power at the receiver. By plotting the CC on a set of surfaces from the source to the receiver, the coupling path, which traces the coupled power flow, can be visualized. All visualization procedures can be performed in a full-wave simulation tool, thus making the proposed method convenient to use. To validate and demonstrate the potential benefits of the new method, visualization of the coupling path in a realistic automotive intentional electromagnetic interference problem is presented. In addition, a mitigation solution based on the visualization result was examined.

Accurate measurements of travel distance and speed are crucial for the analysis of animal movements. Measuring the movements of ants entails measuring the change in locations registered at time intervals. This process involves dilemma of setting the proper time window: a short time window is vulnerable to spatial errors in observation, while a long time window leads to underestimation of the travel distance. To overcome these difficulties, we propose a novel algorithm that successively interpolates two consecutive points of ant’s trajectory for a given time window by embracing the alternating tripod gait of ants. We demonstrate that this algorithm is more reliable compared to the conventional method of travel distance estimation based on the sum of the consecutive straight-line displacements (SLD). After obtaining speed estimates for a range of sampling time windows, we applied a fitting method that can estimate the actual speed without prior knowledge of spatial error distribution. We compared results from several methods of speed and curvature extracted from the empirical data of ant trajectories. We encourage empirical scientists to utilize the proposed methods rather than the conventional SLD method of speed estimation as this process is a more reliable and subjective selection of the sampling time window can be avoided.

In this paper, a dielectric properties extraction method for millimeter-wave applications is presented. Substrate integrated waveguide (SIW) cavity resonators with the same structure and varied thicknesses are employed to separate the dissipation factor (DF) of the substrate material for the cavity resonators. The dielectric constant and loss tangent of the dielectric substrate for the SIW is extracted at the resonance frequencies based on the unloaded Q-factors of transmission loss measurement. The DF from the unloaded Q-factors, which is highly dependent on the thickness of the substrate, is extracted using an iterative fitting process for the substrate thickness estimation without cross sectioning. To validate the extraction method, the SIW cavity resonators are fabricated using RO4003C substrate material and the dielectric properties are extracted in the X-band (8.2 to 12.4 GHz). The extracted thicknesses of the SIW resonators are validated by cross-sectioning. Additionally, the extracted dielectric properties are also verified by comparing the dielectric characteristics of the SIW resonators with the different thicknesses. With the presented method, the time expense for the conventional dielectric characterization method with cross-sectioning is reduced.

The transfer function between the intentional electromagnetic interference (IEMI) attacker and the engine control unit (ECU) circuit in an automobile is extracted to analyze how the IEMI affects the vehicle. A log-periodic antenna is used as the IEMI aggressor based on the frequency domain measurement and the transfer function of the log-periodic antenna is compared with the transfer function of the standard mesoband source generator measured in the time domain. The electric field of the standard source is regenerated with the transfer function of the log-periodic antenna. It is then compared with the original field of the standard source to validate the transfer function of the log-periodic antenna. Since the D-dot sensor is used to measure radiated field in the time domain, a noise in low frequency region is amplified and it is investigated.

Analogies across disciplines often indicate the existence of universal principles such as optimization, while the underlying proximate mechanisms may differ. It was reported recently that trails of ants refract at the border of substrates, on which walking speeds differ. This phenomenon is analogous to the travel-time-minimizing routes of light refracting at the borders between different media. Here, we further demonstrate that ant tracks converge or diverge across lens-shaped impediments similar to light rays through concave or convex optical lenses. The results suggest that the optical principle of travel time reduction may apply to ants. We propose a simple mathematical model that assumes nonlinear positive feedback in pheromone accumulation. It provides a possible explanation of the observed similarity between ant behavior and optics, and it is the first quantitative theoretical demonstration that pheromone-based proximate mechanisms of trail formation may produce this similarity. However, the future detailed empirical observations of ant behavior on impediment edges during the process of pheromone trail formation are needed in order to evaluate alternative explanations for this similarity.

An efficient automotive simulation method for intentional electromagnetic interference (IEMI) is developed. As the full automotive simulation is computationally demanding, running the simulation for all possible IEMI attack locations is prohibitive. Therefore, a new methodology based on the reciprocity theorem is proposed to replace all regular simulations by one special simulation. The special simulation uses the reverse model which is defined by switching the location of source and observation point in the regular automotive simulation model. The reciprocity based simulation is validated by comparing the simulated results with all measured data in the IEMI experiment.

An intentional electromagnetic interference (IEMI) source has been reconstructed by using the dipole moment. The automotive simulations with the equivalent dipole can accurately characterize the costly IEMI experiments. Based on the measurement, the least square method is applied in source reconstruction. Importing the reconstructed source and the full-scale car model in simulation tool, fields inside the car are obtained. By comparing the simulation result with the experiment data, the automotive simulation model for IEMI is validated.

Some defended prey animals can switch on their normally hidden aposematic signals. This switching may occur in reaction to predators’ approach (pre-attack signals) or attack (post-attack signals). Switchable aposematism has been relatively poorly studied, but we can expect that it might bring a variety of benefits to an aposmetic organism. First, the switching could startle the predators (deimatism). Second, it could facilitate aversive learning. Third, it could minimize exposure or energetic expense, as the signal can be switched off. These potential benefits might offset costs of developing, maintaining and utilizing the switchable traits. Here we focused on the third benefit of switchability, the cost-saving aspect, and developed an individual-based computer simulation of predators and prey. In 88,128 model runs, we observed evolution of permanent, pre-attack, or post-attack aposematic signals of varying strength. We found that, in general, the pre-attack switchable aposematism may require moderate predator learning speed, high basal detectability, and moderate to high signal cost. On the other hand, the post-attack signals may arise under slow predator learning, low basal detectability and high signal cost. When predator population turnover is fast, it may lead to evolution of post-attack aposematic signals that are not conforming to the above tendency. We also suggest that a high switching cost may exert different selection pressure on the pre-attack than the post-attack switchable strategies. To our knowledge, these are the first theoretical attempts to systematically explore the evolution of switchable aposematism relative to permanent aposematism in defended prey. Our simulation model is capable of addressing additional questions beyond the scope of this article, and we open the simulation software, program manual and source code for free public use.

A typical colony of Neotropical army ants (subfamily Ecitoninae) regularly raids a large area around their bivouac by forming a narrow directional column that can reach up to one hundred meters in length. The raid is finished and then relaunched 12–17 times, each time toward different orientation. After completing all bouts the colony relocates to a new area. A hypothetical alternative to this foraging mode is raiding radially and symmetrically by expanding the search front in every direction like a circular bubble. Using an existing agent-based modeling software that simulates army ants’ behavior, we compared the two possible modes of foraging in different food distributions. Regardless of the food patch abundance, the radial raiding was superior to the directional raiding when food patches had low quality, and the directional raiding was favorable when the patches were rich. In terms of energy efficiency, the radial raiding was the better strategy in a wide range of conditions. In contrast, the directional raiding tended to yield more food per coverage area. Based on our model, we suggest that the directional raiding by army ants is an adaptation to the habitats with abundance of high-quality food patches. This conclusion fits well with the ecology of army ants.

An STM-4 rate serial data transmitter (SDT) is implemented using a 0.8 μm CMOS process. The charge injection method is adopted for the delay cells in the VCO to enhance the oscillation frequency. By optimizing the combination of NOR gates in the shift register, the delay of the data serializer is reduced. Probable timing errors are avoided by phase reversal of the serial data clock. It dissipates about 700 mW at 624 Mbps.