Faculty of Computer Science and Engineering
Permanent URI for this communityhttps://repository.ukim.mk/handle/20.500.12188/5
The Faculty of Computer Science and Engineering (FCSE) within UKIM is the largest and most prestigious faculty in the field of computer science and technologies in Macedonia, and among the largest
faculties in that field in the region.
The FCSE teaching staff consists of 50 professors and 30 associates. These include many “best in field” personnel, such as the most referenced scientists in Macedonia and the most influential professors in the ICT industry in the Republic of Macedonia.
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Item type:Publication, A 12-Bit 20-kS/s 640-nW SAR ADC With a VCDL-Based Open-Loop Time-Domain Comparator(Institute of Electrical and Electronics Engineers (IEEE), 2022-02) ;Zhou, Xiaochuan ;Gui, Xiaoyan; ; Zhang, YanlongThis brief presents a 12-bit ultra-low-power asynchronous successive approximation register (SAR) analog-to-digital converter (ADC). A voltage-controlled delay line (VCDL) based open-loop time-domain comparator is proposed and analyzed, achieving low noise and ultra-low power performance. By employing the mixed switching scheme, the segmented capacitive digital-to-analog converter (CDAC) arrays as well as the synchronous data-weighted averaging (DWA) calibration block, the proposed SAR ADC can operate from 1.8 V down to 0.8 V at 20–200 kS/s. The designed ADC is fabricated in a 0.18- μm CMOS process and the measurement results show the proposed SAR ADC achieves an SNDR of 65-dB with power consumption of 647 nW from a 0.8 V power supply at 20 kS/s. - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Detection of Premature Heartbeats(IEEE, 2022-05-23)Premature heartbeats are those that appear earlier than the regular ones due to contractions not originating from the Sinus Atrial Node, out of the normal heart rhythm. Although one might think this is a trivial task to detect, the distribution of premature heartbeats in the benchmark electrocardiograms shows it is not the case. We aim at finding the optimal method to detect premature heartbeats, threshold value and context level for temporal based approach. Methodology: Several methods are specified to calculate the relation of the premature heartbeat to a set of several previous instances and conduct experiments to present which averaging method (arithmetic, geometric and harmonic mean) delivers the best solution. Then, we calculate the deviation ratio to the average of these beats that affect the prematurity condition. Particularly, the goal is to find an average AV G of previous k beat-to-beat intervals RR, such that the ratio between the difference dRR of the analyzed RR and AV G versus AV G is more than a specific threshold T hr. Data: The comprehensive MIT-BIH Arrhythmia Electrocardiogram benchmark database is used in our evaluation. The analysis is conducted on the array of beat-to-beat intervals for the heartbeats preceding the premature one. Conclusion: The results show that the optimal method is based on the arithmetic mean AM We found that the larger k, the better performance is achieved. A sufficient performance with F1 score over 85% is achieved for k = 5 and T hr = 15%. - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Comparing AWS Streaming Services: A Use Case on ECG Data Streams(IEEE, 2022-05-23) ;Velickovska, MarijaThe goal of this research paper is to compare Amazon Kinesis Data Streams and SQS via a practical use case for processing electrocardiogram medical data. Both services are tested on a large number of concurrent data streams up to 10.000 concurrent data streams, measuring and evaluating their performance. In both cases, the producer is a programmed data generator that supplies the data to the services. The motivation of the paper is the streaming of textual files with 125-500 samples per second written as integers, representing electrocardiograms from sensors. We set a research hypothesis that Amazon Kinesis will outperform SQS service for streaming medical data collected from sensors. The pros and cons are listed for each of the Amazon services taking into account the price, use cases when each of the services will be more applicable, and the scalability. The concluding results from this experiment are that both of the services provide great performance but they will mainly provide better results if each of them is applied to a specific use case. - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Network Traffic Impact on Cloud Usage at Different Providers(IEEE, 2022-05-23) ;Bidikov, V.; Markozanov, V.The research question focuses on finding an optimal cost-less and efficient solution, analyzing the differences between uploading and downloading data between different cloud solutions. The conducted experiments compare AWS cloud platform offered by Amazon and use two of its products: computational cloud platform EC2 and storage cloud platform S3. We explore three different versions of S3 storage and S3 Standard, each of them with its own purposes, characteristics and costs. Additionally we test the data transfer and computational capabilities of a t2.micro instance of the EC2 virtual machine. Then, we compare the experiment on the European Cloud provider - Scaleway Elements and use two of its products - Virtual Instances based on the Stardust instances for computations and Object Storage a S3 compatible storage platform.We conclude that the network connection between Amazon nodes is far superior than any other, both in performance and costs. Fetching results from an AWS computational service (EC2) is much cheaper and faster when using an AWS platform as an intermediary (S3) compared to a direct transfer to the local machine. We observe a similar superior network performance in the comparison of Scaleway Cloud Infrastructure. - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Detecting Ventricular Beats with Machine Learning Models(IEEE, 2022-05-23) ;Tudjarski, Stojancho ;Stankovski, AleksandarThis paper aims at modeling a classifier of Ventricular heartbeats by experimenting with the most advanced classic binary classifiers in different scenarios for feature engineering. Methodology: The results were acquired based on experimenting with XGBoost and Random Forest algorithms, as two of the most advanced classifiers not based on neural networks. Although the annotated ECG data sets contain records with several heartbeat classes, we focus on a model that would distinguish V from others (Non-V heartbeats). Considering that we are dealing with a highly imbalanced data set, we applied the SMOTE algorithm for data enrichment to provide a better-balanced data set for training the model. To acquire better results, we added new calculated features, with and without feature selection. For feature selection, we used the Fisher Selector algorithm. Data: We used MIT-BIH Arrhythmia benchmark database, with train/test split according to the patient-oriented splitting approach that separates the original dataset into two subsets with approximately equal sizes and distribution of heartbeat types. Conclusion: The best results are achieved with XGBoost algorithm with original feature set. We achieved precision of 91.36%, recall of 88.31% and F1 score of 89.81%. Results showed that oversampling does not provide significantly better overall model performance. Still, we would recommend this approach since in practice, when dealing with imbalanced data sets, this leads to more robust models that perform better with data outside the training and test sets, such as when the model is used in production. - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Parallelization of Dijkstra’s Algorithm for Robot Motion Planning: Is It Worth Increasing Speed Without Losing Accuracy?(IEEE, 2022-11-15) ;Josifoski, Darko; ; This paper examines the problem of parallelizing Dijkstra’s algorithm, as an algorithm for robot motion planning was a challenge to twist the algorithm in such a way so it can be executed in parallel, rather than sequentially. In this paper, we test the validity of a research hypothesis that the speed of Dijkstra’s algorithm can be increased by parallelizing and keeping the same accuracy. The developed use-case of Dijkstra’s algorithm as a robot motion planning algorithm was tested against performance, both in execution speed and accuracy. Finally, we elaborate on the benefits of this parallelizing approach. - Some of the metrics are blocked by yourconsent settings
Item type:Publication, CardioHPC: Serverless Approaches for Real-Time Heart Monitoring of Thousands of Patients(IEEE, 2022-11); ; ;Amza, Andrei ;Hohenegger, ArminProdan, RaduWe analyze a heart monitoring center for patients wearing electrocardiogram sensors outside hospitals. This prevents serious heart damages and increases life expectancy and health-care efficiency. In this paper, we address a problem to provide a scalable infrastructure for the real-time processing scenario for at least 10,000 patients simultaneously, and efficient fast processing architecture for the postponed scenario when patients upload data after realized measurements. CardioHPC is a project to realize a simulation of these two scenarios using digital signal processing algorithms and artificial intelligence-based detection and classification software for automated reporting and alerting. We elaborate the challenges we met in experimenting with different serverless implementations: 1) container-based on Google Cloud Run, and 2) Function-as-a-Service (FaaS) on AWS Lambda. Experimental results present the effect of overhead in the request and transfer time, and speedup achieved by analyzing the response time and throughput on both container-based and FaaS implementations as serverless workflows. - Some of the metrics are blocked by yourconsent settings
Item type:Publication, From Continuous ECG Signals to Extracted Features for Machine Learning Models and Arrhythmia Annotations(IEEE, 2022-11-15) ;Tudjarski, Stojancho ;Stankovski, Aleksandar; This paper describes the process of transforming an ECG signal as a continuous stream of numbers representing measured electrical voltages between the ECG electrodes into an output indicating the existence of arrhythmia. The ECG data stream is a structured array of converted analog signal values to digital data. Although this stream uses a continuous structure of numbers within a given range that depends on the bit resolution during conversion, it is still unstructured as a representation of the appearance of arrhythmia since it does not contain information about detected arrhythmia. This paper presents how to process ECG data, detect heartbeat annotations, and calculate various parameters for tabular-based data with a fixed number of columns to be used as input into ML-based algorithms. Our use case addresses an ML algorithm to detect atrial fibrillation arrhythmia, as an irregular heart rhythm. Practically a set of numbers in the ECG samples, which do not have structured arrhythmia annotations, is transformed into structured annotations. Experiments are conducted on the well-known ECG benchmark MIT-BIH Arrhythmia Database. The input data is resampled from 360 Hz to 125 Hz signal, and a signal processing algorithm is used to detect heartbeats, extracting a fixed set of features, and systematically forwarded to the feature selection ML methodologies to obtain atrial fibrillation annotations. - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Sampling Rate Impact on Heart Rate Variability(IEEE, 2022-11-15); ;Tudjarski, StojanchoAnagelevska, AnaWe set a research question to find the impact of the sampling rate in the electrocardiograms on the calculation of the heart rate variability. Our evaluation method analyzes the heart rate variability on the MITDB electrocardiogram benchmark database originally sampled to 360 Hz. Then the electrocardiogram records are resampled to 125 Hz, and a new set of heart rate variability parameters are calculated and compared to those calculated on 360 Hz. The analysis performed on time-domain heart rate variability parameters showed that the impact of sampling frequency was large for NN50 and pNN50 parameters (up to a max value of 50%, and mean of 10%), and smaller for SDNN and RMSSD (up to a max value of 10%, and an average of 2%). In conclusion, heart rate variability needs a higher sampling frequency to reveal more precise results. - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Effect of Bézier Interpolation on Similarity of Heartbeats in Electrocardiograms(IEEE, 2022-11-15); ;Tonkovikj, LucijaPetrovski, NikolaSampling frequency and bit resolution impact the presentation of heartbeats in electrocardiograms. One of the most challenging tasks in automated medical interpretation is the determination of the heartbeat type, whether the beat was initiated by a normal sequence, or by the ventricle. The usual way to detect the beat class is to analyze the morphological features including shape, width and height of the heartbeat. In this paper, we tackle this problem by checking the similarity of the heartbeats and set a research hypothesis that Bézier interpolation can improve the correctness of the similarity check. We found that the similarity check of two heartbeats can be improved a lot by using Bézier interpolation on the samples around the detected peak.
