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Termites are believed to have evolved in a way that optimizes their foraging efficiency, which involves both searching for food and transporting it efficiently. Although the search efficiency has been well-studied through tunnel pattern analysis, transport efficiency has received limited attention due to the challenges of directly observing behavior that is highly influenced by environmental conditions. In this study, we introduce an individual-based model to simulate transport behavior and examine transport efficiency (E) by considering the tunnel surface irregularities and curvature, which are critical environmental factors. The model is characterized by four control variables: tunnel curvature (k 1), termite stopping time at irregularity sites (k 2), irregularity distribution (k 3), and irregularity density (k 4). The simulation results indicate that as k 1 increases, E decreases, while k 3 has little impact on E. The impact of k 4 on E is decisive; when k 4 ≤ 6, an increase in k 4 results in increased traffic jam frequency and a faster reduction in E. However, when k 4 > 6, the jamming frequency is not significantly affected, reducing the decrease in E. k 2 strongly contributes to reducing E without significantly affecting the frequency. In the discussion section, we explore potential mechanisms that termites use to maintain transport efficiency in heterogeneous soils, and discuss how to improve the model to better reflect real-termite systems. [ABSTRACT FROM AUTHOR]

There are many limitations to applying online spectrum analysis techniques for diagnosis of closed-loop inverter-fed induction motors due to variable load or frequency operation, and the masking effect of the current regulator. In this paper, a new automated approach for testing inverter-fed induction machines for airgap eccentricity is proposed. The main concept is to use the inverter to excite the machine with a pulsating field at multiple angular positions to observe the variation of equivalent impedance due to eccentricity, whenever the motor is stopped. It is shown that the increase in the value of the equivalent (leakage) inductance under standstill excitation can be used as an indicator of increasing airgap eccentricity. Standstill testing can provide reliable assessment of eccentricity that is independent of variations in operating conditions, load interferences, or motor type. An experimental study on a 7.5-hp induction motor verifies that eccentricity can be detected with high sensitivity and reliability without additional hardware. [ABSTRACT FROM PUBLISHER]

A new technique for detecting incipient Inter-laminar insulation failure of laminated stator cores of large generators Is proposed in this paper. The proposed scheme is a low flux induction method that employs a novel probe for core testing. The new probe configuration, which uses magnetic material and is scanned in the wedge depression area, significantly improves the sensitivity of fault detection as well as user convenience compared to existing methods. Experimental results from various test generators tested in factory, field, and lab environments under a number of fault conditions are presented to verify the sensitivity and reliability of the proposed scheme. [ABSTRACT FROM AUTHOR]

Although brushless excitation systems in synchronous machines have reduced the maintenance requirements and brush-related failures, they have increased the operating stresses on the excitation system components. Since the rotating excitation system is not accessible, it is difficult to detect excitation system failures such as open circuit diodes or open armature windings to prevent degradation in machine performance and reliability. Detection of such failures currently relies on monitoring the magnitude and harmonic content of the exciter field current. However, it is desirable to improve the reliability of fault detection with multiple test methods, considering the high cost of brushless exciter testing and repair due to the requirement of machine outage/disassembly. In this work, alternative off-line testing and on-line monitoring options are proposed for detection of excitation system failures. An off-line test based on ac excitation of the exciter field and on-line monitoring based on stator current and airgap flux analysis, are investigated, and fault indicators sensitive to excitation system failures are proposed for reliable fault monitoring. An experimental study on 3.8, 5.5, and 30 kW synchronous machines is given to validate the claims on the sensitivity and reliability of the proposed test methods. [ABSTRACT FROM AUTHOR]

Simple Summary: Subterranean termite colonies can be eliminated using baiting systems. However, for a given bait to be effective, the active ingredient must be lethal at concentrations that are also palatable to termites. The insect molting hormone, 20-hydroxyecdysone (20E), has potential for use in termite baits, but its palatability to termites has not been examined. The purpose of this study was to determine what concentrations of 20E, if any, cause termite workers to feed less readily. To test this, paper disks were treated with various concentrations of 20E. Groups of 1000 termites of three different species; the Formosan, the Asian and the Eastern subterranean termite; were placed in arenas. The termites had the option of following a path to feed on either a paper disk containing the 20E, or an untreated disk, and the amount of paper consumed was then compared. The results showed that the Asian subterranean termite had the least tolerance for the 20E, the Formosan subterranean termite had a reduced tolerance, and the presence of the 20E had no impact on the Eastern subterranean termite. Effective active ingredients in toxicant bait formulations must be non-deterrent to insect feeding behavior at lethal concentrations. This study evaluated feeding deterrence for Coptotermes formosanus Shiraki, C. gestroi (Wasmann), and Reticulitermes flavipes (Kollar) when provided access to cellulose impregnated with various concentrations of the insect molting hormone, 20-hydroxyecdysone (20E). Termites were exposed to 20E concentrations of 200, 500, 1000 and 2000 ppm and to noviflumuron at 5000 ppm in a 24 h choice-test, and the mass of substrate consumption from treated and untreated media pads was compared for each treatment. 20E feeding deterrence was detected at 500, 1000 and 2000 ppm for C. gestroi, and at 2000 ppm for C. formosanus. No significant differences in consumption of treated and untreated substrate was detected at any concentration for R. flavipes. Potential methods for reducing deterrence are discussed. [ABSTRACT FROM AUTHOR]