Miracle-dz/UniFAR-FTUs huggingface dataset:
Personalized Services in Collaborative Learning Environment Based on Learner’s Activity Records

Online learning provides learners with appropriate learning environments and a large amount of various educational resources, while eliminating the constraints of time and space. How to optimize the learning experience for learners has become a top priority. We focus on helping learners choose suitable resources, maintaining their enthusiasm for learning, and preventing them from dropping out. In this paper, we propose a complete solution to address the above challenges. First, we design a semantic online learning environment based on resource-sharing, where learners can perform a variety of learning-related activities (e.g., share, access, and vote), and learners’ processes are described by knowledge graph. Then, we derive learners’ features from their activity records collected by web logs, and form learners’ feature models. Finally, we combine knowledge based embedding with collaborative learning to provide personalized recommendation services for learners.
Analysis and Design of Post-Regulation Stages for Resonant Capacitively-Coupled Wireless Power Systems

This study introduces a power regulation design methodology for power receiving units (PRUs) in capacitively-coupled resonant wireless power transfer (RWPT) systems by using hybrid multi-level (HML) post-regulators. A generic design framework for capacitive RWPT systems with post-regulation stages is developed, followed by a simplified behavioral model for the PRU including the additional regulation stage. It has been demonstrated that by using HML stages for power-regulation, significantly wider impedance matching range can be achieved, which results in better spatial freedom of wireless power systems. This study also covers design tradeoffs between several post-regulators in terms of efficiency, coupling range and conversion range. A 40 W experimental resonant capacitively-coupled WPT system with HML buck (HMLB) post-regulator has been designed and examined up to 150 mm misalignment, at a resonant operation of 3 MHz. A very good agreement is obtained between the theoretical predictions and experimental results.
Intelligent Methods for Test and Reliability

Test methods that can keep up with the ongoing increase in complexity of semiconductor products and their underlying technologies are an essential prerequisite for maintaining quality and safety of our daily lives and for continued success of our economies and societies. There is a huge potential how test methods can benefit from recent breakthroughs in domains such as artificial intelligence, data analytics, virtual/augmented reality, and security. The Graduate School on “Intelligent Methods for Semiconductor Test and Reliability” (GS-IMTR) at the University of Stuttgart is a large-scale, radically interdisciplinary effort to address the scientific-technological challenges in this domain. It is funded by Advantest, one of the world leaders in automatic test equipment. In this paper, we describe the overall philosophy of the Graduate School and the specific scientific questions targeted by its ten projects.
Battery Equalizer for Series-Connected Batteries Based on Half-Bridge LLC Topology

In power grids, electric vehicles, commercial and domestic energy storage systems, lithium-ion batteries are usually used in series or parallel in order to meet the required voltage and power. However, the differences in individual characteristics, which lead to unbalanced battery voltages, affect the life and reliability of the system. In order to solve the problem, this paper proposes a novel voltage equalization circuit based on the half-bridge LLC topology with a multi-port transformer. And the corresponding control strategy is designed to achieve fast equalization. With the control strategy, the circuit can charge batteries with lower voltages quickly at the beginning. Owing to the larger discharging current in the final stage of the equalization, equalizing speed is guaranteed when voltage difference is close to zero. Finally, the experimental results of a 24-cell equalization verify the feasibility and validity of the proposed battery equalizer and control strategy.
SafeDM: a Hardware Diversity Monitor for Redundant Execution on Non-Lockstepped Cores

Computing systems in the safety domain, such as those in avionics or space, require specific safety measures related to the criticality of the deployment. A problem these systems face is that of transient failures in hardware. A solution commonly used to tackle potential failures is to introduce redundancy in these systems, for example 2 cores that execute the same program at the same time. However, redundancy does not solve all potential failures, such as Common Cause Failures (CCF), where a single fault affects both cores identically (e.g. a voltage droop). If both redundant cores have identical state when the fault occurs, then there may be a CCF since the fault can affect both cores in the same way. To avoid CCF it is critical to know that there is diversity in the execution amongst the redundant cores. In this paper we introduce SafeDM, a hardware Diversity Monitor that quantifies the diversity of each redundant processor to guarantee that CCF will not go unnoticed, and without needing to deploy lockstepped cores. SafeDM computes data and instruction diversity separately, using different techniques appropriate for each case. We integrate SafeDM in a RISC-V FPGA space MPSoC from Cobham Gaisler where SafeDM is proven effective with a large benchmark suite, incurring low area and power overheads. Overall, SafeDM is an effective hardware solution to quantify diversity in cores performing redundant execution.
Flux Minimization in Interphase Coupled Inductors of Parallel-Connected Voltage Source Converters

A flux compensation technique is described to significantly lower the peak flux in interphase inductors used to suppress the flow of high-frequency circulating currents between interleaved voltage source converters (VSCs) operating with the discontinuous pulse width modulation scheme (DPWM). The technique described is useful to reduce the required cross-sectional area of interphase inductors, which reduces the size, weight, and material cost of the magnetics in interleaved VSCs. Coupled inductors (CIs) with cross-coupled windings are used to demonstrate the performance of the flux compensation technique using simulation and experimental results of an 11 kW (300Vdc, 208Vac/31A) laboratory prototype. The inductor cross-coupled winding arrangement lowers the effective series inductance of the interphase inductors and makes it possible to produce high-frequency fundamental PWM output voltages with a very low voltage drop across the inductors.
Compressed Sensing based Tow Ship Interference Cancellation and Target Detection in Shallow Ocean

Passive towed arrays assume great importance in coastal surveillance, providing the capability of long range detection and localization of targets. The performance of the towed array sonar is bounded by the intense tow ship radiated signal picked up by the array. This problem is magnified in shallow ocean, owing to the multipath and multimodal propagation of the acoustic waves. A popular solution for mitigating the own platform interference is based on the Eigen analysis of space time covariance matrix (STCM). As length of the sensor array increases, matrix dimension increases, prohibiting the practical realization of this approach. In this paper, a computationally efficient pre-processing technique based on the Compressed Sensing (CS) framework is investigated. The efficacy of the method is initially evaluated with the monte carlo simulations of shallow ocean data model. The scheme is further validated on the experimental data captured during the field trials in the Arabian Sea. It is demonstrated that employing the proposed scheme, tow ship noise is cancelled substantially, aiding the detection of low signal to noise ratio (SNR) targets, while the computational requirements are diminished to a large extent.
Sparse Adaptive Channel Estimation based on l0-PRLS Algorithm for Underwater Acoustic Communications

Underwater acoustic (UWA) channels usually manifest time-varying and sparse properties, motivating channel estimations based on sparse adaptive filtering algorithms. Existing sparse adaptive filtering methods are designed by applying a sparse norm regularization, employing a proportionate updating step size, or combining above two operations. Currently, the least mean squares (LMS) type sparse adaptive filtering algorithms have been extensively investigated for the estimation of UWA channels. In contrast, the recursive least squares (RLS) type methods are much less studied. We recently proposed a RLS-type sparse adaptive filtering algorithm named l1-PRLS, which showed superiority for UWA channel estimation. In this paper, we substitute the l1 norm in l1-PRLS by an approximation of l0 norm, leading to the l0-PRLS algorithm. The l0-PRLS was then applied for sparse channel estimations. Simulation and experimental results are provided to demonstrate its advantage over the standard RLS and its other sparse variants.
Prioritizing Barriers to implement Green Supply Chain in Shiraz Oil Refining Company by FAHP Method

Today, social factors, client's pressures and environment pollution have made the practical use of methods for maintaining the environment as a necessity. The green supply chain management is one of the subjects which help this necessity. Lots of studies have done on this issue but most of them focused on the implementation factors and its stimulus. However, being familiar with the implementation barriers can help its operation. Therefore, the current study aims at identifying the barriers of implementing green supply chain and its prioritization by FAHP fuzzy method. The identified barriers were taken into two groups namely internal organizational group and external organizational group. The present study is practical in terms of goal and it's regarded as a descriptive survey research type in terms of method. The instrument used in this study includes a questionnaire. The statistical population includes managers and experts of Shiraz oil refining company. The statistical sample is a complete enumeration type that includes all society members. After data analysis through FAHP method, it was revealed that the internal barriers (by weight of 0.619) are more important than external barriers (by weight of 0.380). Moreover, infrastructure factors were the most significant factors among internal barriers. On the other hand, market related factors were the most significant factors among external barriers.
AUV-based Quay Wall Inspection Using a Scanning Sonar-based Wall Following Algorithm

Quay wall inspection plays an important role for the safety in harbors and ports. Today it mainly has to be done manually by divers which is time-consuming and only takes place on a random basis. Imaging sensors can be used to help determine the wall condition and assess any damage more accurately. Therefore, a strategy for autonomous quay wall inspection using cooperating Monsun AUVs developed by the University of Lübeck is proposed. A core component is a new real-time scanning sonar-based wall following algorithm that demonstrates high accuracy and robustness in experiments on a typical quay wall.
Fate and impact of Bay of Bengal rivers in an intermediate resolution ocean model

Annually, the Bay of Bengal receives about 1500 km3 of freshwater from the rivers along its boundary. The decrease in salinity caused by the dilution due to river water strengthens the vertical stratification, creates shallow mixed layers, and enables faster SST recovery. The high SST is a factor that promotes cloud formation, monsoon depressions and tropical cyclones over the northern Bay of Bengal. Therefore, understanding the role of river runoff in maintaining the high SST is an important problem, particularly with respect to short range weather forecast. Using a global configuration of the GFDL Modular Ocean Model 5 at a horizontal resolution of about 13 km and 42 vertical layers, we have investigated the impact of river runoff on the upper layer thermo-haline structure and circulation in the north Indian Ocean. Two numerical experiments, one with the river runoff into the ocean excluded and the other by including climatological monthly mean river runoff are carried out for a period of 40 years each, to determine the pathways of river water in the Bay of Bengal and into the Arabian Sea. During summer, the river water is confined in the northern Bay of Bengal, but during winter it flows southward along the western boundary into the Arabian Sea. We have identified that there is significant impact on the sea surface temperature in the northeastern Arabian Sea where the river water causes warming of the sea surface. The change in the northeastern Arabian Sea is linked to the northward advection of low salinity water by the West India Coastal Current (WICC). In the absence of Bay of Bengal rivers, the wintertime East India Coastal Current (EICC) and the WICC, which carry the low salinity river water are weaker. The northward extent of low salinity water along the west coast of India is restricted in the absence of river runoff and consequently, the salinity of the northeastern Arabian Sea tends to be slightly higher. The north eastern Arabian Sea is warmer in the presence of river runoff into the BAy of Bengal. This warming is attributed to the strengthening of the WICC and the northward advection of warmer water when the river runoff is present. The model simulations suggest that the Bay of Bengal rivers have implications to places both near the source region and far into the Arabian Sea where the coastal currents (EICC and WICC) carry the low salinity water.
An Advanced PLL-less Control Scheme for LVRT Capability with Harmonics Current Mitigations in Grid-Tied PV System Under Weak and Distorted Grid

This paper proposes an advanced phase-locked loop (PLL) less control scheme to mitigate the grid current harmonics along with enhanced low voltage ride-through (LVRT) capability of a grid-tied photovoltaic system (GTPVS) under the weak grid and distorted grid voltages. The enhanced LVRT operation of the GTPVS is achieved with the coordinated operation of the active power regulator (APR) and dynamic reactive power support (DRPS) controller. Moreover, an advanced phase compensated multiresonant (APCMR) current controller is utilized to mitigate the grid current harmonics under distorted grid voltages. The proposed control scheme is implemented in the $\alpha\beta$ reference frame without park's transformation as well as a PLL unit. Thus, the computational burden of the proposed control scheme reduces. Further, the frequency adaptability of the GTPVS is improved during variations in grid frequency. To verify and evaluate the effectiveness of the proposed LVRTPLL-less control scheme (LPLCS) over the conventional LVRT PLL based control scheme (LPBCS), the experimental analysis is carried out using OPAL-RT OP 4510 real-time digital simulator.
A Linear Active Disturbance Rejection Control Based Sensor lessControl for IPMSMs Considering Harmonic Current Suppression

This paper presents a linear active disturbance rejection control (LADRC)-based sensorless control for interior permanent-magnet synchronous motor (IPMSM) drives considering harmonic current suppression. Firstly, a LADRC is developed in an estimated synchronously rotating reference frame to directly estimate back electromotive force (EMF), which is treated as a disturbance, without using low-pass filter or switching function. Then, the rotor position and speed are obtained from the estimated back EMF without any phase delay or speed chattering problem. Secondly, the periodically oscillating position estimation error caused by the harmonic current is analyzed and then a novel harmonic current controller based on second order generalized integrator (SOGI) and phase-locked loop (PLL) is proposed to further improve the rotor position estimation performance. Finally, the performance of the proposed LADRC-based sensorless control with harmonic current suppression is validated by simulation results for a 200-W IPMSM drive system.
Variables Decoupling and Multi-objective Optimization for High-power Bidirectional Interleaved Converters in Electric Vehicles

To achieve the best tradeoff between efficiency and power density of high-power interleaved buck-boost converters for electric vehicles, a variables decoupling and multi-objective optimization method is proposed. Different the conventional modeling methods where the efficiency and volume are modeled separately, relationships among variables in the modeling process are firstly decoupled. Based on variables decoupling process in this paper, efficiency and converter volume are modeled as functions of four design variables, namely switching frequency $f_{s}$, phase number $N$, inductor current ripple $\Delta I_{L}$ and inductor core radius $r$ (denoting core cross-area). Within the range of design variables, iterative calculations are performed based on the enumeration method to obtain Pareto-fronts of efficiency and volume, thus acquiring the theoretical optimization results for the tradeoff between efficiency and power density. According to the optimization results, a 60kW IBBC converter was constructed, the power density of the converter reaches 9.6SkW /L, while the highest efficiency is 98.6%.
A Novel Power Combining Strategy for Rectenna Array of Microwave Power Transmission System

To mitigate the effects of the non-uniform RF power distribution, a novel power combining strategy for rectenna array in Microwave power transfer (MPT) system is proposed in this paper. With the benefit of the proposed strategy, the optimal connection pattern of rectenna array can be found under the non-uniform RF power distribution condition, which a few woks have been focused on. As a result, a power loss reduction can be achieved in rectenna array. Moreover, a 5.8GHz MPT system is built to verify the power combining strategy.
Modeling the impact of tropical cyclone Vardah along the Chennai coast

The present study is envisioned to understand the circulation pattern and the storm surge induced by a very severe cyclonic storm, Vardah that made its landfall along the east coast of India on December 2016. The hydrodynamic model, Telemac 2D was applied to examine the water level variations during the extreme event, by generating a high-resolution computational grid. The model was driven by tidal forcing at the ocean boundary. The elevation was considered as a boundary condition in order to understand the interaction of the surge with the tides to examine the variation of the intensity of the surge over the coast. The wind stress as the basic input and wind pressure was applied as a forcing parameter to capture the pressure drop during the cyclonic event. The quality of the wind field is enhanced by applying a parametric cyclone wind model (Holland 1980) with ECMWF wind field. The computed wind speed and surge heights are compared with field measurements. The simulated surge height up to about 1.2m during landfall time is found to follow closely with the field observed data. The wind and tide induced surface elevations are found to be higher and the corresponding flow velocity was high when the surge rises and recedes. The main purpose of this study is to understand the details of the severe tropical cyclone characteristics and to develop a numerical set up that precisely predict the surge heights based on which precautionary measures can be charted out for the future.
High-Frequency LLC Converter with Narrow Frequency Variations for Aircraft Applications

This paper describes the design and implementation of a compact and high-frequency LLC converter with wide input voltage range (from 220 V to 320 V), output power range (from 250 W to 1.5 kW), high efficiency (over 96 % at full power), high power-density (32 kW/dm3) and narrow frequency variations (15 %). A complete and automated optimization process has been developed, including the comparison between different semiconductor technologies and the design of a Matrix Transformer that reduces the height of this magnetic component. A fully customized converter has been developed using an automated design tool.
Highway Decision-Making and Motion Planning for Autonomous Driving via Soft Actor-Critic

In this study, a decision-making and motion planning controller with continuous action space is constructed in the highway driving scenario based on deep reinforcement learning. In the decision-making and planning problem, the goal is to achieve the safety, efficiency, and comfort of automated vehicles. In the driving scenario, the surrounding vehicles are controlled by the intelligent driver model and a general model (minimizing overall braking induced by lane change, MOBIL), which enables them to react to the environment and mimic the vehicle interactions on the highway. Given the uncertainties in the driving conditions, a specific deep reinforcement learning technique, called soft actor-critic, is used to solve the decision-making and planning problem with continuous action space. Simulation results show that the proposed method can solve the decision-making and motion planning problem in the interactive traffic environment to carry out safe lane-change maneuvers and cruise at high speed. In addition, two control policies are developed with different weights on safety, efficiency, and comfort.
Integrated Grid Inductor-Transformer Structure with Reduced Core Loss and Volume for E-Capless Single-Stage EV Charger

This paper presents the design and optimization of an integrated magnetic structure that combines the grid inductors and transformer in the single-stage EV -charger. The proposed integration technique reduces the number of magnetic bodies, hence reducing the cost and total magnetic core loss while increasing the power density. By utilizing the fixed 50% duty cycle operation of the converter, a further reduction in core loss can be achieved resulting in improved light-load efficiency. This paper also presents an analysis of the optimal PCB winding arrangements for the proposed structure to achieve low winding AC loss and stray capacitance. To validate the proposed integrated magnetic structure, a 3.7 kW single-stage AC-DC converter prototype with four different cases of magnetic structures is built. Experimental comparison of these four cases shows that the proposed integrated magnetic structure has higher efficiency and power density compared to the non-integrated ones. U sing the proposed integrated magnetic structure, the core loss that dominates at light-load is improved resulting in an increase of efficiency by 0.9%. At the same time, the proposed integration technique reduces the number of magnetic cores as well as total core volume, reducing the cost and improving the converter power density by up to 11.1 %.