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Learning Body Models:From Humans to Humanoids
Hoffmann, Matěj
2021 - English
Humans and animals excel in combining information from multiple sensory modalities, control-ling their complex bodies, adapting to growth, failures, or using tools. These capabilities are alsohighly desirable in robots. They are displayed by machines to some extent. Yet, the artificial crea-tures are lagging behind. The key foundation is an internal representation of the body that theagent—human, animal, or robot—has developed. The mechanisms of operation of body modelsin the brain are largely unknown and even less is known about how they are constructed fromexperience after birth. In collaboration with developmental psychologists, we conducted targetedexperiments to understand how infants acquire first “sensorimotor body knowledge”. These ex-periments inform our work in which we construct embodied computational models on humanoidrobots that address the mechanisms behind learning, adaptation, and operation of multimodalbody representations. At the same time, we assess which of the features of the “body in the brain”should be transferred to robots to give rise to more adaptive and resilient, self-calibrating ma-chines. We extend traditional robot kinematic calibration focusing on self-contained approacheswhere no external metrology is needed: self-contact and self-observation. Problem formulationallowing to combine several ways of closing the kinematic chain simultaneously is presented,along with a calibration toolbox and experimental validation on several robot platforms. Finally,next to models of the body itself, we study peripersonal space—the space immediately surround-ing the body. Again, embodied computational models are developed and subsequently, the pos-sibility of turning these biologically inspired representations into safe human-robot collaborationis studied.
Available in digital repository of ČVUT.
Learning Body Models:From Humans to Humanoids
Humans and animals excel in combining information from multiple sensory modalities, control-ling their complex bodies, adapting to growth, failures, or using tools. These capabilities are alsohighly ...
FIRE-PROTECTION WITH ALKALI-ACTIVATED CEMENT BINDER
Šejna J.; Šmilauer V.; Šulc S.; Wald F.; Reiterman P.
2021 - English
Fire resistance of unprotected steel structures is very low and steel elements must be protected from fire. One possibility is to create a protective layer of a cement-based material. Most types of cement have a low resistance to high temperatures, reducing mechanical properties. In flammability tests, cement activated with alkaline compounds showed better properties compared to conventional types of cement. This paper represents the determination of the properties of two H-Cement mortars with experlite or fireclay sand. Experiments carried out in a small kiln simulating a 1D load showed differences between elements in terms of heat transfer to the tested elements. The calculation model created to predict the course of the experiments has been validated and the unknown properties of the material have been calculated based on the data collected. The samples were tested in a small fire furnace. Finally, the thermal conductivity pattern was determined depending on the temperature.
Keywords:
fire safety; alkali-activated cement; fire-protection; modelling; material properties
Available in digital repository of ČVUT.
FIRE-PROTECTION WITH ALKALI-ACTIVATED CEMENT BINDER
Fire resistance of unprotected steel structures is very low and steel elements must be protected from fire. One possibility is to create a protective layer of a cement-based material. Most types of ...
Potential Biomarkers From Positive Definite 4th Order Tensors In Hardi
Kaushik S.; Kybic J.; Bansal A.; Tsegey T.; Slovak J.
2021 - English
In this paper, we provide a framework to evaluate new scalar quantities for higher order tensors (HOT) appearing in high angular resolution diffusion imaging (HARDI). These can potentially serve as biomarkers. It involves flattening of HOTs and extraction of the diagonal D-components. Experiments performed in the 4th order case reveal that D-components encode geometric information unlike the isometric 6D 2nd order Voigt form. The existing invariants obtained from the Voigt form are considered for comparison. We also notice that D-components can be useful in segmentation of white matter structures in crossing regions and classification. Results on phantom and the synthetic dataset support the conclusions
Keywords:
Biomarkers; HARDI; Anisotropy
Available in digital repository of ČVUT.
Potential Biomarkers From Positive Definite 4th Order Tensors In Hardi
In this paper, we provide a framework to evaluate new scalar quantities for higher order tensors (HOT) appearing in high angular resolution diffusion imaging (HARDI). These can potentially serve as ...
Key criteria for the short-circuit capability of IGBTs
Treek van, V.; Schulze, H.-J.; Baburske, R.; Hille, F.; Niedernostheide, F.-J.; Pfirsch, F.
2021 - English
Short-circuit behavior and capability are investigated and optimized during IGBT development. Thereby,
knowledge about destruction and high-frequency short-circuit oscillation mechanisms is needed. For the
thermal destruction mechanism, filaments are formed shortly before destruction during the thermal runaway itself, whereas for the electrical destruction mechanism strong current filaments are formed by an
electrical mechanism, before the self-heating in the filaments leads to a thermal runaway. At low
collector-emitter voltages, weak non-destructive filaments exist for a large current range. For both the
filament formation and short-circuit oscillations (SCOs), an electric-field peak in the field-stop layer and
a quasi-plasma layer beneath the MOS cells are mandatory. For SCOs, which are caused by a periodic
storage and release of charge carriers inside the device, additionally, a weak electrical field at the beginning of the drift zone is necessary. Weak, non-destructive filaments and SCOs are likely to occur
simultaneously. An increase of the bipolar current gain reduces the operating area with SCOs and
increases the electrical short-circuit capability. A simultaneous reduction of the thermal short-circuit
robustness can be avoided by advanced p-emitter concepts or (over-)compensated by an improved
thermal setup.
Available in digital repository of ČVUT.
Key criteria for the short-circuit capability of IGBTs
Short-circuit behavior and capability are investigated and optimized during IGBT development. Thereby, knowledge about destruction and high-frequency short-circuit oscillation mechanisms is needed. ...
A Simulation study of 6.5kV Gate Controlled Diode
Gurunath Vishwamitra Yoganath; Quang Tien Tran; Eckel, Hans-Günter
2021 - English
Gate Controlled Diode (GCD) with micro-pattern trench structure, allows charge carrier modulation at
the anode region by gate control. This is utilized to operate the diode at low saturation mode and
desaturate the diode before IGBT turn-on, to achieve a better trade-off. The paper demonstrates the
concept of a silicon bi-polar power diode with micro-pattern trench gate, for 6.5 kV applications.
Thereby, a detailed study of switching behaviour and the switching pattern were conducted, so as to
reduce the overall switching loss and improve the efficiency. The efficiency also depends on the
robustness of the diode, several issues concerning the reverse recovery robustness of the Gate controlled
diode were investigated.
Available in digital repository of ČVUT.
A Simulation study of 6.5kV Gate Controlled Diode
Gate Controlled Diode (GCD) with micro-pattern trench structure, allows charge carrier modulation at the anode region by gate control. This is utilized to operate the diode at low ...
Concentration and size distribution of solid particle emissions from oxy-fuel combustion of biomass in a fluidized bed
Červený O.; Vybíral P.; Hemerka J.; Mareš L.
2021 - English
The presented work summaries results of measurement of solid particle emissions from experimental 30 kW combustion unit, which has been used for research of oxy fuel combustion of biomass in fluidized bed.
Keywords:
solid particle emissions; oxy-fuel combustion of biomass in fluidized bed; impactor; particle size distribution
Available in digital repository of ČVUT.
Concentration and size distribution of solid particle emissions from oxy-fuel combustion of biomass in a fluidized bed
The presented work summaries results of measurement of solid particle emissions from experimental 30 kW combustion unit, which has been used for research of oxy fuel combustion of biomass in fluidized ...
Methodology of Controlled Crack Introduction in Cementitious Materials
Schreiberová H.; Fládr J.; Trtík T.; Chylík R.; Kohoutková A.
2021 - English
Crack formation is a common and generally inevitable phenomenon in the field of concrete structures. On the other hand, the ever-increasing demand for sustainable construction, thus the structures durability, has led researchers to propose and investigate various crack-sealing methods. This study deals with the key aspect of these investigations – the in-vitro creation of cracks. A large number of the conducted studies have been carried out on artificially cracked specimens, and various methodologies of the controlled crack introduction were presented; however, no specific method was clearly preferred. In this paper, several approaches to the crack introduction are applied: cracking through compressive loading, tensile loading, and 3-point bending. Further, different types of specimens are presented: plain concrete, reinforced with short and long steel fibers, and reinforced with steel rod. The achievable crack characteristics, such as widths or its stability over time, are evaluated and compared. This study thus provides valuable overlook of the possible approaches to the controlled crack creation and points out their potential and limitations. Based on the comparisons presented in this paper, the long steel fiber reinforced concrete specimens subjected to 3-point bending are identified as the most appropriate method of crack induction.
Keywords:
concrete; controlled cracking; self-healing; non-destructive testing
Available in digital repository of ČVUT.
Methodology of Controlled Crack Introduction in Cementitious Materials
Crack formation is a common and generally inevitable phenomenon in the field of concrete structures. On the other hand, the ever-increasing demand for sustainable construction, thus the structures ...
Time Delay Model of the Turbine Pressure Water Conduit: Application to the off-the-grid regime control
Fišer J.; Zítek P.; Kuchař M.; Peichl A.; Kučera M.; Kulík P.; Vyhlídal T.
2021 - English
The paper presents modeling the hydro-turbine governing system with delay in application to the turbo-machinery control. The delay originates from the wave phenomenon encountered in the pressure water conduit connected to the turbine. To facilitate the PID control tuning the turbine and conduit model is linearized and it results in linear time delay system referred to as the neutral system. Particularly, the disturbance rejection is achieved by the PID control response to varying power loads. Finally, the application example demonstrates the turbo-machinery control in the off-the-grid regime.
Keywords:
hydro turbine and conduit model; PID; turbo-machinery control; neutral system
Available in digital repository of ČVUT.
Time Delay Model of the Turbine Pressure Water Conduit: Application to the off-the-grid regime control
The paper presents modeling the hydro-turbine governing system with delay in application to the turbo-machinery control. The delay originates from the wave phenomenon encountered in the pressure water ...
Geodesic ray-tracing in white matter fiber crossing region using decomposition of 4th order tensor
Kaushik S.; Tsegey T.; Bansal A.; Slovak J.
2021 - English
The streamline methods in Diffusion tensor imaging (DTI) use principal eigenvectors for tracking white matter fibers. In comparison, the geodesics in a multivalued ray-tracing method are closer to the actual underlying white matter fibers. This method provides multiple solutions in the form of geodesics in a Riemannian space. These geodesics are robust in tracking high curvature structures in the presence of noise. In the DTI modality, the 2nd order tensor fails to model the heterogeneous regions, e.g., crossing/merging fibers. Therefore, the ray-tracing method is limited to guide the geodesics in these regions. This work, as a first step, utilizes 4th order tensor approximation for the white matter regions. Subsequently, a non-linear optimization is performed to decompose 4th order tensors into multiple 2nd order tensors keeping their symmetric positive definite property. We are using the initial fiber directions from the diagonal components of the 4th order tensor and use the 4th order tensor decomposition for fiber tracking. The experimental results on synthetic images show that geodesics can traverse in heterogeneous and high curvature structures.
Keywords:
HARDI; tensors; fiber tracking
Available in digital repository of ČVUT.
Geodesic ray-tracing in white matter fiber crossing region using decomposition of 4th order tensor
The streamline methods in Diffusion tensor imaging (DTI) use principal eigenvectors for tracking white matter fibers. In comparison, the geodesics in a multivalued ray-tracing method are closer to the ...
TCAD Simulation of the Bipolar Degradation in SiC MOSFET Power Devices
Lachichi, A.; Mawby, P.
2021 - English
TCAD Simulation of the Bipolar Degradation in SiC MOSFET
Power Devices
A. Lachichi and P. Mawby, School of Engineering
University of Warwick.
Coventry, United Kingdom
Abstract
Reliability and performance of SiC high power devices are still limited by inherent SiC material defects
despite tremendous progress made to reduce the density of these defects. The bipolar degradation remains
a major challenge for developing high voltage SiC power devices. It is mainly due to the presence of
Shockley-type stacking sequence faults (SFs) within the hexagonal SiC structure lattice, creating 3C-like
SiC regions embedded within the main 4H-SiC structure. In this paper, we present a two dimensional
numerical model of 4H-SiC power MOSFET device in which the drift region of the device is formed by a
4H-3C-4H heterojunction to account for the bipolar degradation. TCAD simulation results showed that
the 3C- nano-layer creates a high resistive layer, effectively preventing the current flows across it, hence
reducing the total active area of the device.
Available in digital repository of ČVUT.
TCAD Simulation of the Bipolar Degradation in SiC MOSFET Power Devices
TCAD Simulation of the Bipolar Degradation in SiC MOSFET Power Devices A. Lachichi and P. Mawby, School of Engineering University of Warwick. Coventry, United Kingdom Abstract ...
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