Theses and Dissertationshttp://nur.nu.edu.kz:80/handle/123456789/8222024-03-28T20:59:49Z2024-03-28T20:59:49ZANALYSIS OF INTERFERENCE IN LFM RADAR DETECTION AND IMAGING IN A MULTI-RADAR ENVIRONMENTNwigbo, Suanuhttp://nur.nu.edu.kz:80/handle/123456789/75902024-02-05T17:00:27Z2023-04-01T00:00:00ZANALYSIS OF INTERFERENCE IN LFM RADAR DETECTION AND IMAGING IN A MULTI-RADAR ENVIRONMENT
Nwigbo, Suanu
Because of the growing use of radio detection and ranging (radar) systems in multiple application sectors, the radars have to be operated on the same or adjacent frequency resources. This frequency overlap can cause interference and impacts the performance of the victim radar. Besides unintended interferences, there could also be intentional interferences. The interference can cause a reduction in the signal-to-noise ratio, introduce ghost targets, and lead to poor detection capabilities of the radar as well as false detections. Thus, interference effects should be compensated to operate the radar in a safe and secure environment.
In this thesis, different types of interference and their impact on traditional linear frequency modulation (LFM) based radio detection and ranging (radar) are investigated through numerical simulation and electronic radar-based experiments. The work has been extended to investigate the imaging of radar-detected objects with the help of the back-projection technique.
In the simulation environment, a multi-radar environment has been created to investigate the effect of external interference radar on the victim radar. Different types of interference waveforms such as LFM, triangular and pulsed waveforms are being considered. It is found that the LFM-based waveform suffers from coherent LFM interference, which can result in the appearance of ghost targets on the range profile. Whereas, non-coherent types of interference increase the noise level, reducing the signal-to-noise ratio, thus adversely impacting the detection accuracy. Thus, a random hopping LFM-based waveform as an alternative to the LFM-based waveform has been proposed as a robust waveform to mitigate interference in a multi-radar environment.
Experimental work with an mm-wave (77GHz-81GHz) radar sensor for detecting targets has been performed, and radar performance metrics such as range and range resolution have been evaluated with the theoretical values.
Through the back-projection algorithm, the imaging of the detected objects has been obtained. Through extensive iteration, it is found that the back-projection with weighting function provides enhanced resolution.
2023-04-01T00:00:00ZHEART SOUND CLASSIFICATION VIA VISION TRANSFORMER MODELSAdilkhanuly, Zhanathttp://nur.nu.edu.kz:80/handle/123456789/75862024-01-26T21:00:16Z2023-11-23T00:00:00ZHEART SOUND CLASSIFICATION VIA VISION TRANSFORMER MODELS
Adilkhanuly, Zhanat
The automatic heart sound classification is an integral part of the early diagnosis
of cardiovascular diseases(CVDs). Even though advances in medical technologies
allow us to diagnose many CVDs, it remains one of the leading causes of death
worldwide due to its absence of symptoms at the initial stages. Thus, there is a huge
demand to develop other methods of identifying heart sound abnormalities that are
less expensive, simple, and applicable. Several audio feature extraction methods, in
combination with classification models, have been developed over time. However,
existing feature extraction methods are sensitive to noise, which negatively impacts
the performance of the heart sound classification model. In addition, there is a strong
need to develop models more sensitive to heart sound abnormalities in patients. In this
work, we address the limitations of extracted features by using spectrogram images
that are taken from Discrete Fourier Transform, and introducing them to Vision
Transformer Model. Results of our experiments on the benchmark of PhysioNet Heart
Sound Dataset show that the proposed method outperforms existing methodologies
with an accuracy of 0.925 and with a sensitivity score of 0.955
2023-11-23T00:00:00ZFABRICATION AND CHARACTERIZATION OF FUNCTIONALLY GRADED MATERIALS: STUDY OF MICROSTRUCTURE IN CENTRIFUGAL COMPACTION AND HOT PRESSING PROCESSESSariyev, Bakytzhanhttp://nur.nu.edu.kz:80/handle/123456789/75832024-02-12T04:21:54Z2023-08-31T00:00:00ZFABRICATION AND CHARACTERIZATION OF FUNCTIONALLY GRADED MATERIALS: STUDY OF MICROSTRUCTURE IN CENTRIFUGAL COMPACTION AND HOT PRESSING PROCESSES
Sariyev, Bakytzhan
In recent times, remarkable progress in science and technology has prompted scientists to create a new category CCP of structural materials with enhanced characteristics. Functionally graded materials (FGMs) are a new type of composite materials made up of two or more components that are continuously varied in their distribution. The idea of FGMs can be utilized to exploit the advantageous properties of each constituent phase and adjust the distribution of material properties to achieve the desired response to specific mechanical and thermal loads or to modify natural frequencies in a desired manner. To fully utilize the exceptional properties of FGMs in the development of new products, it is essential to conduct fundamental studies on the mechanics of these materials, as well as research on their processing.
The first study investigates the application of centrifugal force for the compaction of metal powders. Aluminium alloy powder with a particle size less than 100 µm and polymer binder were mixed and compacted in the centrifugal machine with varying degrees of centripetal acceleration. SEM micrographs of the green bodies' microstructure showed significant packing densities and an increase in median particle size at sites further from the centrifuge's centre of rotation. The segregation phenomena was not observed at 700 G, but clear particle segregation was found at higher centrifugal forces. This investigation focuses on the development of topologically complex FGM by controlling interfacial microstructure through CCP-based compaction.
The second study examines poly(ether-ether-ketone) (PEEK) and graphite-based high-performance laminate composite materials. The structural, thermal, and mechanical characteristics of the composites, which were created utilising the hot press technique at temperatures below 310°C, were carefully examined and described. SEM images indicated a strong interfacial contact between PEEK and graphite. This research focuses on the design of PEEK/graphite FGM with topologically complex multi-scale compositions and revealed improved mechanical and thermal properties due to the synergistic effect of incorporation of two dissimilar materials under high temperature and joining load.
Overall, this dissertation provides insights into the design and fabrication of materials with multi-scale topologies. The research focuses on understanding the interfacial behaviour of materials at various scales and developing fabrication methods to produce materials with desired properties.
2023-08-31T00:00:00ZGLULA: LINEAR ATTENTION BASED MODEL FOR EFFICIENT HUMAN ACTIVITY RECOGNITION FROM WEARABLE SENSORS AND SKELETON DATABolatov, Aldiyarhttp://nur.nu.edu.kz:80/handle/123456789/75822024-01-10T21:01:15Z2023-01-01T00:00:00ZGLULA: LINEAR ATTENTION BASED MODEL FOR EFFICIENT HUMAN ACTIVITY RECOGNITION FROM WEARABLE SENSORS AND SKELETON DATA
Bolatov, Aldiyar
Sensors’ data is used in monitoring patient activity during rehabilitation and also can
be extended to controlling rehabilitation devices based on the activity of the person.
Both wearable sensors and extracted skeleton data from the video can be used for that.
As there, exist similarities, a unified solution can be presented, which also focuses on
effectively capturing the spatiotemporal dependencies in the data collected by these
sensors and efficiently classifying human activities. With the increasing complexity
and size of models, there is a growing emphasis on optimizing their efficiency in terms
of memory usage and inference time for real-time usage and mobile computers. There
is an opportunity to develop a novel unified framework that incorporates recent advancements
to enhance speed and memory efficiency, specifically tailored for Human
Activity Recognition (HAR) tasks. In line with this approach, we present GLULA, a
unique architecture for human activity recognition. GLULA combines gated convolutional
networks, branched convolutions, and linear self-attention to achieve efficient
and powerful solutions. Extensive experiments showed its effectiveness both in wearable
sensors’ data and skeleton-based sets. Tests were conducted on five benchmark
IMU datasets: PAMAP2, SKODA, OPPORTUNITY, DAPHNET, and USC-HAD.
Our findings demonstrate that GLULA outperforms recent models in the literature
on the latter four datasets but also exhibits the lowest parameter count among stateof-
the-art models. In HAR for the human skeleton domain, examinations were done
on the NTU RGB+D dataset. While getting comparable results with recent work in
this field, it managed to be smaller and significantly faster.
2023-01-01T00:00:00ZDESIGN AND ENGINEERING OF ADVANCED SI-BASED THIN FILM ANODE MATERIALS FOR LI-ION BATTERIESMukanova, Aliyahttp://nur.nu.edu.kz:80/handle/123456789/75792023-12-29T21:00:30Z2019-06-17T00:00:00ZDESIGN AND ENGINEERING OF ADVANCED SI-BASED THIN FILM ANODE MATERIALS FOR LI-ION BATTERIES
Mukanova, Aliya
Lithium-ion batteries (LIBs) are a versatile way of energy conversion and storage. Thin film batteries are the next generation of Li-ion battery technology with the thickness of tens μm and aimed to power a diverse range of microdevices. In order to increase the storage possibility, i.e. capacity, of such batteries, new high capacity electrode materials should be developed. Silicon-based materials are the most promising anodes due to the highest theoretical capacity and a low potential. However, the current drawbacks of Si such as significant volume expansion, electrical contact loss, and low conductivity impede its practical application in LIBs and commercialization. In this doctoral thesis, the research has been performed in two main directions in order to improve the existing microbatteries and find a way to develop a stable Si-based thin film electrode.
The first direction is an investigation of novel silicon carbide thin film (3C-SiC) with a cubic lattice as an anode for LIBs. The advanced method of "single" particle measurement for studying the electrochemical properties of an individual microparticle provided the new data which allowed suggesting the mechanisms of lithiation/delithiation in 3C-SiC film. The use of XRD, TEM, XPS, Raman spectroscopy confirmed that there was no degradation of the 3C-SiC crystal lattice. The obtained results demonstrated that there are in two possible reasons of 3C-SiC thin film electrochemical activity, an intercalation or a capacitance.
The second direction is the design of the three-dimensional (3D) amorphous Si (a-Si) thin film anode. The improvement of a-Si thin film anode was achieved through studying the effects of substrate surface condition, dopants incorporation, electrolyte additive and addition of graphene (GF) underlayer. The designed n-type doped porous a-Si thin film and 3D a-Si/GF anode exhibited high electrochemical performance in the lithium cells for several hundred cycles.
2019-06-17T00:00:00ZBLACK HOLE/MOVING MIRROR CORRESPONDENCE IN (1+1)-DIMENSIONSMyrzakul, Aizhanhttp://nur.nu.edu.kz:80/handle/123456789/75772023-12-29T21:00:26Z2023-11-10T00:00:00ZBLACK HOLE/MOVING MIRROR CORRESPONDENCE IN (1+1)-DIMENSIONS
Myrzakul, Aizhan
The Hawking effect predicts that black holes can emit particles and energy when quantum mechanical effects are taken into account in quantum atmosphere around the black hole. However, certain models of black holes emit infinite energy and infinite particles that are contradictory to both classical and quantum theories' laws. These and other black hole evaporation problems along with the need to get experimental verification have underscored the need for analog and toy models that can solve the issues without losing the essential physical properties of the black hole radiation processes.
The significance of studying moving mirrors is that they are accelerated boundaries that create energy, particles, and entropy similar to black holes. In fact, moving mirrors, which are simplified (1+1)-dimensional versions of the dynamical Casimir effect, act as toy models for black hole evaporation, in some cases, with an exact correspondence to the amount of particle production. Moreover, the dynamical Casimir effect has been measured in the laboratory within the framework of moving mirror model providing experimental observations and insight into the effect, whereas Hawking radiation from black holes effectively can not be measured because the effect is too small.
The general and physically relevant connections of moving mirrors to black hole physics is a prime focus of this thesis. Here black holes and some cosmological models are approximated by (1+1)-dimensional moving mirrors. The detailed and complete investigation of all existing moving mirror models, their classifications and specific characters are the main objectives. This extensive study allows one to distinguish the moving mirror solutions that most physically describe black hole evaporation. They have proven capability to solve specific issues related to Hawking radiation. A new model related to the Schwarzschild black hole that solves the issue of finite energy with respect to Hawking radiation is developed. Also, it is established that Callan-Giddings-Harvey-Strominger (CGHS) black hole model has a correspondence to the exponentially accelerated moving mirror in coordinate time for the particle production. In addition, the mirror radiation power and radiation reaction force, that have recently been derived, have been applied to the specific moving mirror model of the CGHS correspondence. As a result, it is shown that Larmor power and self-force for the mirror describe quantum radiation. Furthermore, two distinct methods of deriving the stress tensor for the quantum radiation of the moving mirror are analyzed and a comparison analysis is made. Finally, while extensively studying all the known moving mirror solutions and trying to compile collective results, some new results have been found, including some trajectories in null and spacetime coordinates, particle count for the mirrors that have finite particle production, fluxes for some mirrors in certain coordinates that have interesting physical effect, and etc.
All existing moving mirror solutions are studied by classification into several types based on their dynamics. Then, each mirror is extensively reviewed from four perspectives: dynamics, flux & energy, particles, and entropy. These methodologies enable one to obtain a complete set of solutions, understand their behavior, and unveil particular implications and physical features of the moving mirror model as a whole.
2023-11-10T00:00:00Z