SummaryMastication as we all know has always been related to its primary function of digestion, but little do we know that it produces an enhancing effect on general health, especially the cognitive performance related aspects of memory. Recent studies have shown its association with activation of various brain regions, however little is known about its effects on neuronal activity in these specified regions. According to the enormous evidences collected so far, mastication has proved to be effective in conducting huge amount of sensory information to the brain, and maintaining learning and memory functions of hippocampus. Therefore it is essential that we maintain normal occlusion and preserve the masticatory function as long as possible to prevent the attenuation of hippocampus, caused by occlusal disharmony and reduced mastication. We provide an overview on how mastication activates various cortical areas of the brain and how an increase in the cerebral blood oxygen level of hippocampus and prefrontal cortex (PFC) accentuates the learning and memory process. We also justify why maintaining and establishing a normal occlusion is important from neurological point of view.
Analyzing the interactions between transmission and distribution (T&D) system is becoming imperative with the increased penetrations of distributed energy resources (DERs) on electric power distribution networks. An assessment of the impacts of distribution system connected DERs on the transmission system operations is required especially pertaining to system unbalance when modeling both T&D systems. In this paper, a coupled T&D analysis framework is developed through co-simulation approach. The framework utilizes legacy software to separately solve the decoupled T&D models. The T&D interactions are captured by exchanging network solutions at the point of common coupling (PCC). The proposed co-simulation framework adopts an iterative coupling approach resulting in a co-simulation model close to a stand-alone T&D platform. The proposed framework is tested using IEEE-9 bus transmission system model and EPRI's Ckt-24 test distribution feeder model. A case study in which the IEEE 9 bus model interfaced with three ckt24 models is also presented to demonstrate the scalability of the approach. The conditions of convergence by exchanging the boundary variables at the PCC are examined in detail using several case studies with varying levels of load unbalance.
With the increased penetrations of distributed energy resources (DERs), the need for integrated transmission and distribution system analysis (T&D) is imperative. This paper presents an integrated unbalanced T&D analysis framework using an iteratively coupled co-simulation approach. The unbalanced T&D systems are solved separately using dedicated solvers. An iterative approach is developed for T&D interface coupling and to ensure convergence of the boundary variables. To do so, analytical expressions governing the T&D interface are obtained. First-order and second-order convergent methods using Fixedpoint iteration (FPI) method and Newton's method, respectively are proposed to solve the system of nonlinear T&D interface equations. The proposed framework is tested using an integrated T&D system model comprised of 9-bus IEEE transmission test system integrated with a real-world 6000-bus distribution test system. The results show that the proposed framework can model the impacts of system unbalance and increased demand variability on integrated T&D systems and converges during stressed system conditions. As expected, Newton's method converges faster with a fewer number of iterations as compared to FPI method and the improvements are more pronounced during high levels of system unbalance and high loading conditions.
The critical need to model and analyze transmission and distribution (T&D) systems together, given the increasing levels of distributed energy resource (DER) penetrations, has led to the development of several T&D co-simulation platforms, both commercial and open-source. The strength of coupling between the T&D system dictates the accuracy of the co-simulation studies; however, higher accuracy comes at the cost of the increased computational burden. The objective of this paper is to (1) systematically model the different coupling protocols, viz. decoupled (DC), loosely coupled (LC), and tightly coupled (TC), for quasi-static T&D co-simulation studies; and (2) thoroughly compare the three T&D coupling protocols for their accuracy and computational efficiency. The T&D coupling protocols are evaluated for varying system parameters such as DER variability, load unbalances, DER penetration, and size of T&D network. It is observed that the accuracy of both DC and LC models deteriorate with increasing the: (1) system unbalance, (2) DER penetration and variability, and (3) number of T&D coupling points. The results further highlight the need for a tightly coupled (TC) protocol as the T&D system gets more stressed due to the influx of DERs. INDEX TERMS Co-simulation, integrated transmission-distribution analysis, co-simulation coupling strength, tightly-coupled model, distributed energy resources.
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