Ing. Michal Štepanovský, Ph.D.

Článek

10.1016/j.forsciint.2023.111765

Katedra teoretické informatiky
Katedra počítačových systémů

This work presents an automated data-mining model for age-at-death estimation based on 3D scans of the auricular surface of the pelvic bone. The study is based on a multi-population sample of 688 individuals (males and females) originating from one Asian and five European identified osteological collections. Our method requires no expert knowledge and achieves similar accuracy compared to traditional subjective methods. Apart from data acquisition, the whole procedure of pre-processing, feature extraction and age estimation is fully automated and implemented as a computer program. This program is a part of a freely available web-based software tool called CoxAGE3D. This software tool is available at https://cox-age3d.fit.cvut.cz/ Our age-at-death estimation method is suitable for use on individuals with known/un-known population affinity and provides moderate correlation between the estimated age and actual age (Pearson's correlation coefficient is 0.56), and a mean absolute error of 12.4 years.& COPY; 2023 Elsevier B.V. All rights reserved.

Stať ve sborníku

Katedra počítačových systémů

Abstract—This paper presents a RISC-V based computer system simulator, QtRVSim (https://github.com/cvut/qtrvsim), designed for teaching and learning computer systems principles. The simulator allows students to run assembly programs and observe the instruction execution on single-cycle and pipelined microarchitectures. The simulator graphically displays the major components in the datapath, including the register file, the arithmetic-logic unit, memory caches, peripherals, and the control unit with control signals. QtRVSim is free and open-source software available on GitHub and as a WebAssembly application online. For additional materials and related computer architecture projects, see https://comparch.edu.cvut.cz/.

Článek

10.1038/s41598-022-13983-8

Katedra teoretické informatiky
Katedra počítačových systémů

Age-at-death estimation of adult skeletal remains is a key part of biological profile estimation, yet it remains problematic for several reasons. One of them may be the subjective nature of the evaluation of age-related changes, or the fact that the human eye is unable to detect all the relevant surface changes. We have several aims: (1) to validate already existing computer models for age estimation; (2) to propose our own expert system based on computational approaches to eliminate the factor of subjectivity and to use the full potential of surface changes on an articulation area; and (3) to determine what age range the pubic symphysis is useful for age estimation. A sample of 483 3D representations of the pubic symphyseal surfaces from the ossa coxae of adult individuals coming from four European (two from Portugal, one from Switzerland and Greece) and one Asian (Thailand) identified skeletal collections was used. A validation of published algorithms showed very high error in our dataset-the Mean Absolute Error (MAE) ranged from 16.2 and 25.1 years. Two completely new approaches were proposed in this paper: SASS (Simple Automated Symphyseal Surface-based) and AANNESS (Advanced Automated Neural Network-grounded Extended Symphyseal Surface-based), whose MAE values are 11.7 and 10.6 years, respectively. Lastly, it was demonstrated that our models could estimate the age-at-death using the pubic symphysis over the entire adult age range. The proposed models offer objective age estimates with low estimation error (compared to traditional visual methods) and are able to estimate age using the pubic symphysis across the entire adult age range.

Článek

10.1109/COMST.2019.2895817

Katedra počítačových systémů

Micro-electro-mechanical systems (MEMS)-based cross-connects are widely used for all-optical switching in recent optical networks. This paper provides a brief overview of various photonic switching technologies and a detailed review of the working principles, actuating mechanisms, and architectures of MEMS-based optical cross-connects (OXCs) from the last two decades. New approaches, which, potentially, will be adopted in the next generation of MEMS-based cross-connects are also described. The switching MEMS-based cross-connects speed can vary from less than 1 mu s to tens of ms depending on the chosen switching mechanism and actuator parameters. This paper describes the various types of actuators used to manipulate the optical signal inside all-OXCs. Optical properties (insertion loss, crosstalk), switching speed, and scalability are also discussed.

Článek

10.1016/j.forsciint.2018.03.047

Katedra teoretické informatiky
Katedra počítačových systémů

The assessment of age-at-death is an important and challenging part of investigations of human skeletal remains. The main objective of the present study was to apply different mathematical approaches in order to reach more accurate and reliable results in age estimation. A multi-ethnic dataset (n = 941) of evaluated age-related changes on the pubic symphysis and the auricular surface of the hip bone was used. Two research groups examined nine different mathematical approaches. The best results were reached by Multi-linear regression, followed by the Collapsed regression model, with MAE values of 9.7 and 9.9 years, respectively, and with RMSE values of 12.1 and 12.2, respectively. The mean accuracy of decision tree models ranged between 30.7% and 72.3%, with the model using only the PUSx indicator performing the best. Moreover, our results indicate that the limiting factor of age estimation can be the visual evaluation of age-related changes. Further research is required to objectify the proposed methods for estimating age. (c) 2018 Elsevier B.V. All rights reserved.

Článek

10.1016/j.sna.2017.11.007

Katedra počítačových systémů

Various phenomena are emerging in existing micro-electro-mechanical systems (MEMS). In order to fully exploit the potential of such systems, a synergy of multiple engineering fields should be reached through a careful analysis of the designed system and its optimization. It is common practice that complex multi-physics finite element method (FEM)-based models are created to analyze the system. Nevertheless, without a clear understanding of the occurred phenomena, an optimal design will be hard to attain. In this paper, we demonstrate that only minimal design changes in existing MEMS actuators can potentially lead to noticeable improvements of the system. We present a case study considering an electrostatic rotational parallel-plate actuator under sliding mode control. This type of actuator is one of the most successful commercial examples of this actuator widely applied in MEMS-based optical switches. The results of this paper confirm that the control strategy of the actuator is a substantial part of the system and should be taken into account; specifically, it can affect the parameters of the designed actuator in order to modify the dynamics of the system in a desired way. In our case, this can reduce the amplitude of output chattering or reduce the switching time of the actuator. Moreover, this paper points out various design flaws, namely when synergy between various system requirements was not reached successfully and only a suboptimal solution was discovered.

Stať ve sborníku

Katedra teoretické informatiky
Katedra počítačových systémů

This paper compares traditional averages-based model with other various age estimation models in the range from the simplest to the advanced ones, and introduces novel Tabular Constrained Multiple-linear Regression (TCMLR) model. This TCMLR model has similar complexity as traditional averages-based model (it can by evaluated manually), but improves the mean absolute error in average about 0.30 years (approx. 3.6 months) for males, and 0.18 years (approx. 2.2 months) for females, respectively. For all models, the chronological age of an individual is estimated from mineralization stages of dentition. This study was based on a sample of 976 orthopantomographs taken of 662 boys and 314 girls of Czech nationality aged between 2.7 and 20.5 years.

Stať ve sborníku

10.1109/INFORMATICS.2017.8327264

Katedra počítačových systémů

All-optical switching fabrics based on the Micro-Electro-Mechanical Systems (MEMS) technology are now widely available on the market. This paper reviews working principles and architectures of MEMS-based optical switches from the past to the present day. During the last two decades, many approaches and actuating mechanisms emerged. In general, optical MEMS-based switches can employ movable micromirrors as basic switching element, or movable couplers (resonators). The switching speed can vary from less than 1µs to tens of ms. This paper briefly describes principles of all of these switches. Optical properties (insertion loss, crosstalk) and switching speed are also discussed.

Článek

10.1016/j.forsciint.2017.08.005

Katedra teoretické informatiky
Katedra počítačových systémů

In order to analyze and improve the dental age estimation in children and adolescents for forensic purposes, 22 age estimation methods were compared to a sample of 976 orthopantomographs (662 males, 314 females) of healthy Czech children and adolescents aged between 2.7 and 20.5 years. All methods are compared in terms of the accuracy and complexity and are based on various data mining methods or on simple mathematical operations. The winning method is presented in detail. The comparison showed that only three methods provide the best accuracy while remaining user-friendly. These methods were used to build a tabular multiple linear regression model, an M5P tree model and support vector machine model with first-order polynomial kernel. All of them have mean absolute error (MAE) under 0.7 years for both males and females. The other well-performing data mining methods (RBF neural network, K-nearest neighbors, Kstar, etc.) have similar or slightly better accuracy, but they are not user-friendly as they require computing equipment and the implementation as computer program. The lowest estimation accuracy provides the traditional model based on age averages (MAE under 0.96 years). Different relevancy of various teeth for the age estimation was found. This finding also explains the lowest accuracy of the traditional averages-based model. In this paper, a technique for missing data replacement for the cases with missing teeth is presented in detail as well as the constrained tabular multiple regression model. Also, we provide free age prediction software based on this wining model.

Článek

10.1016/j.osn.2016.04.007

Katedra počítačových systémů

The 3D MEMS optical switch utilizes highly reflective micromirrors to manipulate an optical signal inside the switch directly without any conversions, offering bit rate and data protocol independency. As indicated by the simulation results of this paper, many of developed micromirrors (by various companies) are not optimized well in the sense of dynamic behavior and can be further improved. This non-optimal design negatively limits the switching speed of the optical switch. The switching mechanism is in a fact the two-way coupling between the mechanical structure (micromirror) and electrostatic field (electrodes) - see e.g. Ananthasuresh [1, Sec. 11.4]. This introduces additional effects resulting in coupled rotation of the micromirror about its axes - the cross-axis coupling effect. Existing solutions are mainly focused on the optimization of the control strategy of the micromirror aiming to suppress its oscillations and to minimize the switching time. Our approach is foremost focused on the optimization of dynamic characteristics of the micromirror. This suppress negative effects of cross-axis coupling and thus allows further reduction of the switching time of the switch. Our results are supported by simulation experiments, which consider the switching element as multiphysics system described by partial differential equations.

Stať ve sborníku vyzvaná či oceněná

Katedra počítačových systémů

Recent micro-electro-mechanical systems (MEMS) use various principles and phenomena in order to provide required functionality. Due to the interdisciplinary nature of such systems, their design is often a difficult and complex task requiring knowledge from multiple engineering fields. The main complexity in the design is to provide the system with the necessary abilities and to identify possible design drawbacks. In this paper, we demonstrate that the synergy of multiple engineering fields can be reached through the analysis of the designed system and its optimization. In presented case study, we consider an electrostatic parallel-plate actuator. This type of actuator is one of the most successful commercialized examples of this actuator widely applied in MEMS-based optical switches. As indicated by the simulation results of this paper, many of existing actuator designs have not their dynamic characteristics sufficiently optimized, and therefore, they do not fully exploit the potential of such systems. Our results are supported by simulation experiments, which consider the electrostatic actuator as multiphysics system described by partial differential equations.

Článek

10.1515/comp-2016-0010

Katedra počítačových systémů

Existing 3D MEMS-based optical switches offer good optical properties (low insertion loss, low crosstalk), high reliability and low power consumption. These switches utilize highly reflective micro-mirrors to manipulate an optical signal inside the switch directly without any conversions. They are used to build dynamically reconfigurable, highly-scalable physical optical network layer. As indicated by the simulation results of this paper, many of existing micro-mirror designs do not have their dynamic characteristics well optimized and this limits the switching speed of the optical switch. In a 3DMEMS switch, the coupling between the mechanical structure (micro-mirror) and electrostatic field (electrodes) results in dynamic coupled rotation of the micro-mirror about its axes, known as the cross-axis coupling effect. The coupling nature of micro-mirror rotation makes its control difficult. In this paper,we present the simulation case studies and a simple optimization technique leading to decoupled rotation of the micro-mirror about two perpendicular axes. This helps to reduce the switching time of the switch while keeping the same manufacturing process and only minimal design changes.

Stať ve sborníku

10.1109/Informatics.2015.7377834

Katedra počítačových systémů

The 3D MEMS optical switches are able to build dynamically reconfigurable, highly-scalable physical layer and to provide a required growing network bandwidth and agility for various service providers, datacenters, cloud computing networks, etc. The switch utilizes highly reflective miniature mirrors to manipulate an optical signal inside the switch directly without any conversions. Nevertheless, as indicated by the simulation results of this paper, many of developed mirrors are not optimized in the sense of dynamic behavior well. The coupling nature of mirror rotation makes its control difficult. In this paper, we present a simple optimization technique leading to decoupled rotation of the mirror about two perpendicular axes.