The Unfolding of the Relational Operant: A Real-time Analysis Using Electroencephalography and Reaction Time Measures

The current study attempted to capture in real time the unfolding of the relational operant using electroencephalography (EEG) and reaction time measures. Participants were exposed to relational pretraining to establish the contextual cues of Same and Opposite for two arbitrary stimuli. These cues were then used to establish a series of contextually controlled discriminations in order to create a simple relational network among a series of arbitrary stimuli. During the test for derived relations of Same and Opposite, EEG and reaction time measures were recorded for each individual test task during the acquisition of a stable derived relational response pattern. Participants were then exposed to an identical set of relational training and testing tasks with the important difference that an entirely different set of stimuli was used. EEG and reaction time measures were again recorded during the relational test phase. Results showed that reaction times decreased for all subjects across successive test tasks and from the first to the second stimulus set. EEG data also suggested that there was increasingly less higher cognitive activity during the derivation of successive stimulus relations within and across stimulus sets. Taken together these findings provide support for the idea that derived relational responding can be viewed as an operant activity that both develops and generalizes

Connection between dynamics and thermodynamics of liquids on the melting line

The dynamics of a large number of liquids and polymers exhibit scaling properties characteristic of a simple repulsive inverse power law (IPL) potential, most notably the superpositioning of relaxation data as a function of the variable TV{\gamma}, where T is temperature, V the specific volume, and {\gamma} a material constant. A related scaling law, TmVm{\Gamma}, with the same exponent {\Gamma}={\gamma}, links the melting temperature Tm and volume Vm of the model IPL liquid; liquid dynamics is then invariant at the melting point. Motivated by a similar invariance of dynamics experimentally observed at transitions of liquid crystals, we determine dynamic and melting point scaling exponents {\gamma} and {\Gamma} for a large number of non-associating liquids. Rigid, spherical molecules containing no polar bonds have {\Gamma}={\gamma}; consequently, the reduced relaxation time, viscosity and diffusion coefficient are each constant along the melting line. For other liquids {\gamma}>{\Gamma} always; i.e., the dynamics is more sensitive to volume than is the melting point, and for these liquids the dynamics at the melting point slows down with increasing Tm (that is, increasing pressure).Comment: 20 pages, 8 figures, 1 tabl

‘Infinity Gate Sensor’: a Differential Magnetic Field Sensor for Measuring Gate Current of SiC Power Transistors

For silicon power devices, gate current measurement has been shown to provide a means of inferring temperature and degradation, and it is important for active gate driving. However, in silicon carbide circuits, gate current measurement is challenging due to interference from switching-induced noise and the required low insertion impedance. This paper presents a low-cost, miniature magnetic field current sensor with 500 MHz bandwidth, that has been optimised for high noise immunity, to allow the accurate measurement of gate current for fast-switching SiC devices. Experimental results from 800 V, 10 A and 1200 V, 50 A double-pulsed bridge leg circuits switching at 80-100 V/ns show a high correlation with gate current measurements using current sense resistors and a 1 GHz optically-isolated voltage probe. The sensor’s gain is 0.67 V/(A/ns) and its insertion inductance is 3.5 nH at 100 MHz. Magnetic pickup from the adjacent power circuit is seen to contribute less than 1% of the overall measurement, and dv/dt susceptibility is quantified through measurement. The theory behind the operation of the sensor, the design principles, the manufacturing detail, and the signal post-processing requirements are presented, providing the user with an alternative to expensive optically isolated probes, and a method of measuring gate current when the addition of a sense resistor is not viable

Instrumentation Requirements for Fast 130+ V/ns Switching of 1700 V, 35 mΩ SiC MOSFETs

This paper demonstrates the benefits, downsides, and instrumentation requirements of switching 1.7 kV, 35 mΩ SiC MOSFETs at 130+ V/ns, beyond the speed used by the device manufacturer for datasheet characterisation. Experimental results are obtained in a 1200 V, 50 A bridge leg, and comparisons are made between passive voltage probes, optically isolated differential probes, shunt current measurement, Rogowski coils, and Infinity Sensors. At 130 V/ns, a 24% improvement over the datasheet characterised switching loss is found, however the limitations of Rogowski coils and passive probes become significant. The methods demonstrated should permit design engineers to explore switching speed and efficiency limitations in their applications

Harvesting Intensity and Aridity Are More Important Than Climate Change in Affecting Future Carbon Stocks of Douglas-Fir Forests

Improved forest management may offer climate mitigation needed to hold warming to below 2°C. However, uncertainties persist about the effects of harvesting intensity on forest carbon sequestration, especially when considering interactions with regional climate and climate change. Here, we investigated the combined effects of harvesting intensity, climatic aridity, and climate change on carbon stocks in Douglas-fir [Pseudotsuga menziesii Mirb. (Franco)] stands. We used the Carbon Budget Model of the Canadian Forest Sector to simulate the harvest and regrowth of seven Douglas-fir stand types covering a 900 km-long climate gradient across British Columbia, Canada. In particular, we simulated stand growth under three regimes (+17%, −17% and historical growth increment) and used three temperature regimes [historical, representative concentration pathways (RCP) 2.6 and RCP 8.5]. Increasing harvesting intensity led to significant losses in total ecosystem carbon stocks 50 years post-harvest. Specifically, forests that underwent clearcutting were projected to stock about 36% less carbon by 2,069 than forests that were left untouched. Belowground carbon stocks 50 years into the future were less sensitive to harvesting intensity than aboveground carbon stocks and carbon losses were greater in arid interior Douglas-fir forests than in humid, more productive forests. In addition, growth multipliers and decay due to the RCP’s had little effect on total ecosystem carbon, but aboveground carbon declined by 7% (95% confidence interval [−10.98, −1.81]) in the high emissions (RCP8.5) scenario. We call attention to the implementation of low intensity harvesting systems to preserve aboveground forest carbon stocks until we have a more complete understanding of the impacts of climate change on British Columbia’s forests