Framework for Content-Based Image Identification with Standardized Multiview Features

Rik Das,Sudeep Thepade,Saurav Ghosh 한국전자통신연구원 2016 ETRI Journal Vol.38 No.1

Information identification with image data by means of low-level visual features has evolved as a challenging research domain. Conventional text-based mapping of image data has been gradually replaced by content-based techniques of image identification. Feature extraction from image content plays a crucial role in facilitating content-based detection processes. In this paper, the authors have proposed four different techniques for multiview feature extraction from images. The efficiency of extracted feature vectors for content-based image classification and retrieval is evaluated by means of fusion-based and data standardization–based techniques. It is observed that the latter surpasses the former. The proposed methods outclass state-of-the-art techniques for content-based image identification and show an average increase in precision of 17.71% and 22.78% for classification and retrieval, respectively. Three public datasets — Wang; Oliva and Torralba (OT-Scene); and Corel — are used for verification purposes. The research findings are statistically validated by conducting a paired t-test.

Design Aspects of a Medium-Voltage Direct Current (MVDC) Grid for a University Campus

F. Mura,Rik. W. De Doncker 전력전자학회 2011 ICPE(ISPE)논문집 Vol.2011 No.5

Today’s power systems use alternating current (ac) for transmission and distribution of electrical energy, although the first grids were based on direct current (dc). Due to the absence of appropriate equipment to change voltage levels dc technology did not become widely accepted and was finally ruled out by the more efficient ac infrastructure. However, as a result of considerable technical progress, high-voltage direct current (HVDC) transmission has found its way back into power systems. At lower voltage and power levels medium-voltage dc (MVDC) distribution has been proposed for offshore wind farms and industrial applications. This paper describes the design of an MVDC grid for the interconnection of high-power test benches at a university campus. Voltage control within the dc grid as well as the behavior in different fault scenarios is analyzed using numerical simulations. To assess the environmental impact of the grid the magnetic flux density emitted by the dc cable lines is calculated.

A Single-Phase, Zero-Torque, Drivetrain Integrated On-Board Charger Control Method for Plug-In Hybrid and Electric Vehicles

Murat Senol,Rik W. De Doncker 전력전자학회 2015 ICPE(ISPE)논문집 Vol.2015 No.6

The drivetrain components of an electric vehicle can be utilized to obtain an on-board battery charger (OBC) to save cost, volume and weight. Many integrated OBC topologies have been proposed in the past years, which involve a wide range of machine types, inverter topologies, and power levels. None of these ideas provide a universally acceptable alternative due to the disadvantages they inherit. Therefore, ”drivetrain integrated on-board chargers” is still an interesting research topic. In this paper a single-phase, zero-torque integrated on-board charger control method, which utilizes the machine inductance very effectively and requires minimal intrusion to an existing drivetrain design with a 3-phase permanent-magnet synchronous machine and a three-phase inverter for plug-in hybrid and electric vehicles is investigated.

Discrete Implementation Aspects for Online Current- and Voltage-Sensor Offset Calibration based on Inverter Voltage Distortion

Michael Schubert,Rik W. De Doncker 전력전자학회 2019 ICPE(ISPE)논문집 Vol.2019 No.5

Electrical drive systems without dedicated speed transducer require precise information about the terminal phase voltage to achieve acceptable low-speed performance. Recently, voltage-sensing techniques have gained in importance as they improve stability at low-speeds compared to the conventional estimation from the reference values. But, the additional sensors increase the sensitivity to sensor-offset drift, which can cause self-sensing control algorithms to fail at very low speeds. A novel online offset calibration method was introduced, which compensates for this drawback and offers full decoupling from the control algorithm. Using a pair of phase current and voltage sensors, the dead-time-related inverter voltage-distortion curve is measured continuously. Its point-symmetrical nature is utilized for sensor-offset detection. This way, both sensor offsets can be calibrated continuously during operation and for each phase individually. This paper addresses implementation aspects to achieve deterministic calibration dynamics. A step by step description of the calibration algorithm is given. The method is evaluated through measurements performed on a test bench for an electric-vehicle traction drive.

Design and Realization of a Credit Card Size Driver Stage for High Power Thyristor Based Devices with Integrated MOS Structure

Michael Bragard,Jan Gottschlich,Rik W. De Doncker 전력전자학회 2011 ICPE(ISPE)논문집 Vol.2011 No.5

The Emitter Turn-off Thyristor (ETO) is an advantageous concept in sense of a MOS gated thyristor device. The innovative integration of the MOSFETs inside the press-pack housing allows a cable connection between the high power device and the external gate driver. After a short introduction, this paper focuses on the design and the realization of the external driver stage. Besides a mechanical and thermal decoupling of the driver from the high voltage device, the advantages are an extremely compact design in credit card dimensions. Today’s IGCT solutions require typically A4 format (210 ㎜ x 297 ㎜). Measurements of the prototype prove a significant lower power consumption, which stays far below 5 W at all operating conditions. Additional functionality is demonstrated by short circuit detection and handling.

Integration of High Leakage Inductance Transformers Utilizing Genetically Optimized Curved Foil Windings

David Bundgen,Andre Thonnessen,Rik W. De Doncker 전력전자학회 2023 ICPE(ISPE)논문집 Vol.2023 No.-

In this paper, a transformer design with a magnetic shunt is proposed to achieve an efficient transformer with a precisely defined stray inductance. Highly compact transformer with a precise stray inductance are needed in highly compact dual-active-bridge and resonant converter topologies. To avoid additional eddy currents induced by the inserted shunt, 3D printed bobbins are utilized to shape the stray flux and consequently omit additional eddy currents in the windings. The transformer is simulated with a FEM-Tool and additional loss calculations. The simulation results are used as input parameters for a genetic optimizer to find suitable core and copper geometries. A design is selected from the optimization and a prototype of the transformer is realized. Finally, measurement results are presented to verify the simulations. In comparison to a non-optimized design, the optimized copper windings can reduce the AC-short-circuit resistance by 5.92 %.

Design of a Closed-Loop Control to Balance Unequal Temperature Distributions of Parallel-Connected SiC MOSFETs

Christoph Ludecke,Niklas Fritz,Rik W. De Doncker 전력전자학회 2023 ICPE(ISPE)논문집 Vol.2023 No.-

In this work, a gate driver is presented that allows to balance the temperature of parallel-connected silicon carbide (SiC) metal-oxide-semiconductor field-effect transistors (MOSFETs) with a closed-loop control. In conventional gate drivers, switching events are often slowed down to avoid unevenly distributed losses of parallel-connected SiC MOSFETs. Due to the reduced switching speed, wide-bandgap (WBG) semiconductor devices are not fully utilized. The presented gate driver selectively delays the individual gate signals of the parallel-connected MOSFETs to influence the switching losses. To balance the temperature of the MOSFETs during operation, a closed-loop control is designed and verified by measurements. The presented gate driver thus enables a balanced stress of parallel-connected MOSFETs and a uniform aging of the MOSFETs. Therefore, the potential of parallel-connected WBG semiconductor devices can be better utilized and a derating of the system is avoided.

Role of the Gastrocnemius Musculocutaneous with a Propeller Style Skin Flap in Knee Region Reconstruction: Indications and Pitfalls

Sapino Gianluca,Osinga Rik,Maruccia Michele,Guiotto Martino,Clauss Martin,Borens Olivier,Guillier David,di Summa Pietro Giovanni 대한성형외과학회 2023 Archives of Plastic Surgery Vol.50 No.6

Background Soft tissue reconstruction around the knee area is still an open question, particularly in persistent infections and multiple reoperations scenario. Flap coverage should guarantee joint mobility and protection, even when foreign materials are implanted. The chimeric harvesting of the musculocutaneous gastrocnemius flap, based on the sural artery perforators, can extend its applicability in soft tissue reconstruction of the upper leg, overcoming the drawbacks of the alternative pedicled flaps.Methods A multicenter retrospective study was conducted enrolling patients who underwent to a pedicled, chimeric gastrocnemius musculocutaneous–medial sural artery perforator (GM-MSAP) or lateral sural artery perforator (GM-LSAP) flap for knee coverage in total knee arthroplasty (TKA) recurrent infections and oncological or traumatic defects of the upper leg from 2018 to 2021. Outcomes evaluated were the successful soft tissue reconstruction and flap complications. Surgical timing, reconstruction planning, technique, and rehabilitation protocols were discussed.Results Twenty-one patients were included in the study. Nineteen GM-MSAPs and 2 GM-LSAPs were performed (soft tissue reconstruction in infected TKA [12], in infected hardware [4], and in oncological patients [5]). Donor site was closed primarily in 9 cases, whereas a skin graft was required in 12. Flap wound dehiscence (1), distal flap necrosis (1), distal necrosis of the skin paddle (1), and donor site infection (1) were the encountered complications. Flap reraise associated to implant exchange or extensive debridement was successful without requiring any further flap surgery.Conclusion The propeller–perforator GM-MSAP offers qualitative defect coverage and easiness of multiple flap reraise due to skin availability and its laxity.

Evaluation of Methods for the Operation of PMSM without Position Sensor

Stefan Koschik,Daniel van Treek,Rik W. De Doncker 전력전자학회 2011 ICPE(ISPE)논문집 Vol.2011 No.5

This paper presents an analytical evaluation of sensorless methods for the operation of permanent magnet synchronous machines. The influence of position estimation errors on the stability of a current controller and the deviation of the actual current value from the reference current are considered. Taking these effects into consideration, a flux estimator and a signal injection method are analyzed. Accuracy estimations and design guidelines for the implementation of the two methods are given.

Empirical temperature-based estimates of variability in the oceanic uptake of CO₂over the past 2 decades

Park, Geun-Ha,Lee, Kitack,Wanninkhof, Rik,Feely, Richard A. American Geophysical Union 2006 Journal of Geophysical Research Vol.111 No.c7