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We consider a communication system where two transmitters wish to exchange information through a central relay. The data is assumed to be transmitted over synchronized, average power constrained additive white Gaussian noise channels with a real input with signal-to-noise ratio (SNR) of snr. It has been shown that using lattice codes and lattice decoding, a rate of 1/2 log_2(1/2 plus snr) can be obtained asymptotically, which is essentially optimal at high SNR. However, there has been a lack of practical encoding/decoding schemes for the above mentioned system. We address this issue in this thesis by developing encoding/decoding strategies for the bidirectional relaying system using low-dimensional lattice codes. Our efforts are aimed at developing coding schemes which possess low computational complexity while at the same time providing good performance. We demonstrate two schemes using low-dimensional lattice codes. Both these schemes have their own advantages and are suitable for different classes of lattice codes. The two schemes are tested with different lattices and their performance is compared to that of other schemes for bidirectional relays. The first scheme is termed as demodulate and forward and it essentially consists of performing optimal estimation at the relay. It is primarily implemented with lattice codes of low rate and possesses low decoding complexity. When used with a two-dimensional hexagonal lattice, it achieves a gain of around 3.5 dB in comparison to other schemes like Analog network coding. The second scheme is the sphere decoding scheme which has been implemented with high-rate lattice codes. The sphere decoder is a low-complexity decoder which is used for decoding to a lattice point at the relay. We observe that as the dimensionality of the lattice code is increased, the performance of the sphere decoder for the bidirectional relay gets consistently better. The sphere decoder is also used at high SNR for those instances in which the low density lattice code(LDLC) decoder makes an error and it is found that the sphere decoder can correct around 90 percent of these errors at an SNR of 9.75 dB.

Spiking neural networks (SNNs) are a more biologically realistic model of the brain than traditional analog neural networks and therefore should be better for modelling certain functions of the human brain. This thesis uses the concept of deriving an SNN from an accepted non-spiking neural network via analysis and modifications of the transmission function. We investigate this process to determine if and how the modifications can be made to minimize loss of information during the transition from non-spiking to spiking while retaining positive features and functionality of the non-spiking network. By comparing combinations of spiking neuron models and networks against each other, we determined that replacing the transmission function with a neural model that is similar to it allows for the easiest method to create a spiking neural network that works comparatively well. This similarity between transmission function and neuron model allows for easier parameter selection which is a key component in getting a functioning SNN. The parameters all play different roles, but for the most part, parameters that speed up spiking, such as large resistance values or small rheobases generally help the accuracy of the network. But the network is still incomplete for a spiking neural network since this conversion is often only performed after learning has been completed in analog form. The neuron model and subsequent network developed here are the initial steps in creating a bidirectional SNN that handles hetero-associative and auto-associative recall and can be switched easily between spiking and non-spiking with minimal to no loss of data. By tying everything to the transmission function, the non-spiking learning rule, which in our case uses the transmission function, and the neural model of the SNN, we are able to create a functioning SNN. Without this similarity, we find that creating SNN are much more complicated and require much more work in parameter optimization to achieve a functioning SNN.

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In an attempt to generalize previous models of the bidirectional vortex mean flow, a new solution is presented that can cope with arbitrary injections and outlet conditions. In the process, the steady, inviscid and axisymmetric equations of motions are reduced to one partial differential equation for the stream function, known as the Bragg-Hawthorne equation, which is solved exactly. The solution is shown to be highly dependent on the imposed boundary conditions: the mean flow changes according to the manner by which the fluid is injected or extracted from the vortex chamber. From the stream function, the velocity is obtained along with the vorticity and pressure distributions which are carefully derived and analyzed. The results are then compared to several inviscid models found in the literature. After determining an exact inviscid solution to the problem, viscous effects at the core are added to overcome the known singularity that arises at the centerline. The governing equations are hence revisited while keeping the viscous diffusion term in the tangential momentum equation. The core region, where viscous effects lead to the onset of a forced vortex, is rescaled using appropriate transformations. An asymptotic approximation is then applied to linearize and solve the resulting ODE for the tangential vi velocity. The inner viscous solution is then matched to the outer inviscid result using Prandtl’s Matching Principle. Finally, the viscous correction is passed onto the vorticity and pressure formulations.

In Model-Driven Engineering bidirectional model transformations emerged as an important ingredient to cope with scenarios such as change propagation, synchronization and to keep consistent system views whenever changes occurring on some view have to be propagated over the others. However, bidirectional mappings open a number of intricate issues that have been only partially solved by research. This master thesis identifies a set of features characterizing bidirectional transformations and validates them against two existing approaches. In particular, a benchmark based on the UML2RDBMS transformation and consisting of two different configurations is implemented by means of two different approaches, such as Triple Graph Grammars and the Janus Transformation Language, for understanding bidirectional transformations with respect to the elicited features.

We studied the effects of varying perturbation magnitude and direction on the postural control process of the central nervous system (CNS) caused by perturbation, before and after sensory loss. The electromyogram (EMG) response to a postural perturbation can be composed by a weighted sum of the center of mass (CoM) kinematics. We extended an existing CoM feedback model which predicted EMG of one muscle for unidirectional perturbations; we used recorded data of bidirectional perturbations, which caused muscle activity in anterior as well as posterior muscles. Modeling the CNS as two delayed feedback controllers, we reconstructed the EMGs of two antagonistic muscles simultaneously that were recorded during postural perturbation experiments on cats. Minimizing the error between predicted and recorded EMG and CoM kinematics, we were able to identify controller gains that would result in the best prediction of the recorded EMGs. We hypothesized that the weights on the CoM kinematics remained constant independent of variations in perturbation magnitude or reversed perturbation direction. We applied our model to data from bidirectional perturbations with varying magnitude, with which the cats were perturbed for a short time in one direction and a longer time in the opposite direction. The gains showed small variation for EMG predictions following long perturbations; however, the prediction of EMG following the initial displacement resulted in large gain variations. We showed that these variations were caused by our optimization methods, which was not able to consistently identify controller gains for short initial movements. Using the weights identified for unidirectional perturbations, we were able to predict muscle activity for both directions with the same gains. This suggests that the weights of the CoM kinematics for each muscle did not change for varying perturbation magnitude. We conclude that varying EMG shapes were induced solely by the variation of the CoM kinematics. We repeated the investigations on data that was recorded from cats suffering from sensory loss and found reduced CoM acceleration feedback.

A bidirectional charge equalization circuit based on a bidirectional flyback converter topology is proposed to achieve the balance charging and discharging in series-connected battery bank. The circuit comprises a multi-input transformer, in which the batteries bank are connected to the primary windings via associated active power switches. During discharging, the batteries transfer energy to the load by activating the primary power switches. On the contrary, the batteries are charged by activating the secondary power switch in which the load is replaced by a power source. In order to simplify the control circuit and provide a flexible modulation, a digital signal processor (DSP) with the associated sensors and interface circuits are used as the control kernel. It is used to monitor the variations of battery voltages, and to regulate the duty ratio of the converter to provide a balance charging or discharging among the batteries. A battery bank with four series connected lead-acid batteries is used for illustrating the operation of the bidirectional charge equalization circuit. The experimental results advocate the applicability of the proposed approach.

Indiana University-Purdue University Indianapolis (IUPUI) / The problem behavior theory suggests that the engagement in one problematic behavior increases the likelihood of engagement in another problematic behavior. Previous research has found among youth an increasing probability of co-occurring dieting and substance use behavior, particularly among girls. However, to date findings are inconclusive on the temporal ordering of these behaviors. Further, limited research has been conducted to explore whether the temporal ordering of the two behaviors exist similarly between White and Black youth. The present study will use a cross-lagged panel design across one year to examine the temporal ordering between dieting behavior and substance use among a sample of 2,016 adolescent females (grade mean=7; 77.2% White; 22.8% Black). We hypothesized that a bidirectional relationship would be observed between the two behaviors. However, given no published studies on this relationship by race, no a priori hypotheses were made for this second aim. Result showed that within the full sample dieting behavior significantly predicted substance use one year later, but the inverse relationship was not found. Additionally, this effect was replicated in the White sample but null effects in both directions was found among Black youth. These findings provide support for a temporal relationship between dieting behavior and substance use, such that the former predicts risk for the latter. Moreover, although there is evidence of race differences in the risk pathway, further research is needed to confirm this effect. Future studies are also needed to determine whether this observed temporal relationship is present among adolescent females of other racial/ethnic groups, as well as if the relationship varies as a function of other demographic variables, such as age (e.g., early, mid, or late-adolescence).

This thesis consists of a comprehensive review of bidirectional charging technology, with focus on understanding the technical requirements and the challenges that has to be overcome to standardize this innovation. The thesis is based on three main objectives or goals that is needed to be able to answer the main review question which is: What does it take to standardize, develop and make bidirectional charging a reliable technology? The first objective is to review and explain how the technical bidirectional charging ecosystem works. It starts by explaining in detail how bidirectional charging works and looking closely at how the charging station, electric vehicle (EV), and the power grid connect and work together. The second objective consist of exploring the challenges and the benefits of bidirectional charging. The main challenges explored are social challenges, regulatory challenges, technical challenges and battery degradation. The main benefits explored in this thesis are: offloading the power grid, environmentally friendlier benefits, economic benefits and better management of renewable home systems. The third and final objective in this thesis covers a surveying of existing bidirectional charging products and solutions like Fords F-150 lightning V2G technology and CHAdeMO 2.0. Explaining what they are and their potential success in the European market. The thesis concludes by addressing and discussing the central researched question, which indicates that bidirectional charging is still a young technology that needs to overcome many challenges and improve in some areas before it can be widely used by consumers in a safe and effective way. The results show that the speed and success of the development of this technology depend on how well the actors and stakeholders cooperate with each other and how fast the regulations and standards evolve. EU and Swedish regulations need to keep developing standards for better interoperability. This will help create a legislation for independent market players and key stakeholders, making it easier for them to interact and make compatible products. Therefore, the research done in this thesis suggests that in order to standardize bidirectional charging, different actors, stakeholders and regulatory organizations need to work together better in the future to make V2X safe, standardized and interoperable. There are very few V2G solutions available for customers today, but with the cooperation of key actors, new ISO standards and EV manufacturers making more compatible cars, this technology has the potential to become more accessible in the upcoming years.