DSpace Repository

Nazarbayev University Repository (NUR) is an institutional electronic archive designed for the long-term preservation, aggregation, and dissemination of scientific research outcomes and intellectual property produced by the Nazarbayev University community and affiliated organizations.

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001. Theses 3168
002. NU Research Publications 11760
003. NU Research Institutes & Centres 586
004. NU Journals & Magazines 285
005. Forums, Conferences & Projects 1332

Recent Submissions

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Design and Development of Integrated Perovskite Photovoltaic Energy Harvesting System for Internet-of-Things and Building-Integrated Photovoltaic Applications
(Nazarbayev University School of Engineering and Digital Sciences, 2026-03) Olzhabay, Yerassyl; Ng, Annie; Shafiee, Mehdi; Ukaegbu, Ikechi A.; Ishak, Dahaman
As global energy demand increases, the growing emphasis on sustainable solutions has driven significant interest in advanced energy harvesting technologies. Perovskite solar cells (PSCs) are the third-generation photovoltaic (PV) technology that exhibits promising power conversion efficiency (PCE) under both indoor and outdoor illumination conditions. Despite their short lifetimes, PSCs demonstrate remarkable characteristics, including high efficiency, low-cost production, flexibility, color tunability, and semitransparency. There are many energy harvesting circuits available on the market, optimized for silicon PV, which makes up the majority of the PV market. However, using such circuits with PSCs will result in suboptimal performance due to differences in the properties of the perovskite material. Therefore, it is essential to develop PSCs with suitable circuits carefully. This thesis investigates the design, development, and experimental validation of a PSC-based system, with a focus on powering the Internet of Things (IoT) and building-integrated photovoltaic (BIPV) applications. This work proposes power consumption optimization for the selected potential IoT application to minimize energy consumption important for autonomous systems. On the other hand, a bus stop shelter has been proposed as a potential BIPV application to demonstrate the operational concept of the energy harvesting system platform. The theoretical model of the proposed system has been simulated in MATLAB (2021b) Simulink software. For both lighting conditions, the prototypes demonstrated high performance, achieving 99.9% tracking accuracy and more than 90% converter efficiency in simulations. The proposed energy harvesting system is experimentally validated by fabricating working prototypes and conducting physical testing with large PSCs fabricated in our laboratory. The experiment results show a minimum MPPT efficiency of 95.4%, while converter efficiencies of 62% and 73% were achieved for indoor and outdoor cases, respectively. A scenario with high converter efficiency (80 – 90%) demonstrates the proper operation of the designed converter. The large 30 cm × 30 cm PSC module was used with a buck converter setup to supply a load of up to 2352 mW at 84% conversion efficiency. The findings highlight the potential of PSCs to provide sustainable energy solutions in varied lighting conditions, thereby contributing to advancements in renewable energy technologies for autonomous systems.
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From Waste to Medicine: Flow Engineering for Lignocellulosic-Based API Synthesis
(Nazarbayev University School of Engineering and Digital Sciences, 2026-04-30) Megbenu, Harry Kwaku; Nuraje, Nurxat; Shah, Dhawal; Shaimardan, Minanar; Balu, Alina Mariana
The growing demand for active pharmaceutical ingredients (APIs) continues to reinforce global dependence on fossil-derived feedstocks and energy-intensive batch manufacturing, contributing to greenhouse gas emissions and unsustainable carbon flows. In response to climate targets and circular bioeconomy principles, this doctoral thesis develops continuous flow chemistry strategies for converting waste lignocellulosic biomass (LCB) into high-value chemicals and essential medicines. Locally sourced corncob and rice husk collected from agricultural sites in Kazakhstan were employed as renewable feedstocks. A controlled formic acid pretreatment enabled selective extraction of hemicellulosic sugars, which were subsequently converted into furfural (FF) in a continuous flow millireactor using a ZnCl2/NaCl catalytic system in an IPA:H2O solvent mixture. Under optimized conditions (170 °C, 10 min residence time), FF yields reached 44% from corncob and 27% from rice husk, demonstrating efficient valorization of locally available biomass resources. Building upon biomass-derived FF, an integrated multistep continuous-flow route was developed for the synthesis of prazosin. The sequence comprised oxidation of FF to 2-furoic acid (90% yield, 99% conversion under optimal flow conditions), amide coupling to form 1-(2-furoyl)piperazine (71% yield), regioselective amination of the quinazoline intermediate (70% yield), and final C–N bond formation under intensified flow conditions. Optimization of solvent composition, temperature, and residence time enabled prazosin formation in a THF:MeOH system with an isolated yield of 82%, significantly shortening reaction time while maintaining high selectivity and operational stability. In parallel, continuous-flow synthesis of furosemide from 2,4-dichloro-5-sulfamoylbenzoic acid and furfurylamine was systematically optimized. Solvent screening identified THF as the most suitable medium for flow operation, avoiding precipitation and ensuring stable flow. At 180 °C and 30 min residence time with 3 equivalents of furfurylamine, the system achieved a maximum isolated yield of 79% with 87–93% substrate conversion. These results demonstrate improved selectivity and controlled thermal management relative to conventional batch methodologies. Computational investigations using density functional theory (DFT) provided mechanistic insight into key bond-forming steps, rationalizing observed reactivity trends and supporting experimental optimization. Preliminary sustainability evaluation further suggests that coupling renewable feedstocks with continuous manufacturing reduces solvent inventory, enhances energy efficiency, and improves overall process safety.
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Investigation of powder-based directed energy deposition for multi-material manufacturing
(Nazarbayev University School of Engineering and Digital Sciences, 2026-05-19) Otynshiyev, Yeldar
Interest in additive manufacturing (AM) has expanded rapidly, with Directed Energy Deposition (DED) emerging as a prominent technique for fabricating large-scale components, refurbishing parts, and enabling multi-material deposition. Powderbased DED is governed by a complex interplay of physical phenomena, including particle–particle, particle–gas, and particle–wall interactions within the nozzle, as well as particle–laser interactions during melt pool formation. When dissimilar metallic materials are used, additional challenges arise from differences in particle density, morphology, flowability, thermal properties, melting behavior, and interfacial reactions. Therefore, understanding powder delivery, interfacial formation, and melt pool behavior is essential for improving the stability and reliability of multi-material DED processes. This thesis investigates powder-based DED for multi-material manufacturing through three connected studies. The first study investigates the powder stream behavior of two dissimilar metal powders, stainless steel SS316L and bronze CuSn10, during powder feeding through a coaxial DED nozzle. High-speed imaging combined with particle image velocimetry is employed to characterize the powder stream geometry and the particle velocity distribution under different processing conditions. The influence of powder feeding rate, carrier gas flow rate, and shielding gas flow rate on the focal distance, stream waist, and convergence angle of the powder stream is systematically analyzed. Image-processing techniques are used to extract the geometric characteristics of the powder stream, enabling a quantitative comparison between the two powder materials. The results reveal distinct differences in particle flow behavior due to variations in particle density, size, and morphology, highlighting the critical role of gas flow parameters in controlling powder stream stability and delivery efficiency....
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Harvesting Basic Oxygen Furnace Slags As Construction Materials Using CO2 Mineralization And Geopolymerization Processes
(Nazarbayev University School of Engineering and Digital Sciences, 2026-04-30) Tukaziban, Aizhan; Shon, Chang-Seon; Kim, Jong Ryeol; Zhang, Dichuan; Chung, Chul-Woo
Basic oxygen furnace slag (BOFS) is an industrial by-product that is generated during the steelmaking process. Its chemical composition is similar to blast furnace slag, which is widely used in clinker production. However, the principal difference is that BOFS contains free calcium oxide (f-CaO) and free magnesium oxide (f-MgO) in its chemical composition. In the presence of water, these free metal-bearing oxides experience volumetric expansion, which causes dimensional instability. Consequently, the utilization of BOFS as a construction material remains challenging. In Kazakhstan, the utilization rate of BOFS is particularly low. The large-scale stockpiling of BOFS in landfills might lead to several environmental issues and pollution. The limited application of BOFS in the local construction industry is primarily due to its inherent volumetric instability arising from f-CaO and f-MgO. Moreover, there is a lack of effective stabilization of BOFS techniques and the absence of a standardized protocol for the application of BOFS as a construction material in Kazakhstan, which constitutes a significant research gap. This study addresses these challenges through a systematic approach aimed at improving the stability and practical utilization of BOFS in construction materials. CO₂ mineralization is a chemical reaction between CO₂ and metal-bearing oxide minerals. During natural weathering, BOFS undergoes carbonation, in which reactive free CaO and MgO gradually react with atmospheric CO₂ and moisture, reducing their reactivity and stabilizing expansion behavior. For this reason, the potential of long-term stockpiled BOFS was investigated as a naturally aged and partially stabilized material. To further enhance dimensional stability and immobilize the remaining reactive phases, geopolymerization was used to form a dense binding matrix around BOFS particles. A performance-based kinetic model was then developed as a practical tool to optimize mixture parameters and determine the minimum alkali activator content required to control harmful expansion. Finally, based on the optimized conditions, mixture designs were developed for practical construction applications, particularly non-autoclaved geopolymer cellular bricks and geopolymer Controlled Low Strength Material (CLSM) incorporating treated BOFS as aggregate...
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Hysteresis of Soil-water Characteristic Curve for Soil with Bimodal Grain-Size Distribution
(Nazarbayev University School of Engineering and Digital Sciences, 2026-03-02) Bello, Nura; Kim, Jong Ryeol; Satyanaga, Alfrendo; Gofar, Nurly
Many regions are characterized by residual soils which are often gap-graded and are associated with dual porosity and a bimodal grain size distribution. Gap-graded soils also exhibit bimodal unsaturated hydraulic properties, therefore, its interaction with moisture is unique. To effectively address geotechnical challenges associated with these soils, it is essential that their geotechnical analyses incorporate the soil properties, to realistically represent actual soil behavior and field conditions. Changes in soil moisture during drying (from evaporation) and wetting (from precipitation and snowmelt) and pore suction generally affect the overall soil's behavior. The most important soil parameter that illustrates the link between the water content in the soil pores and the associated soil suction is the Soil-Water Characteristic Curve (SWCC). The soil moisture conditions throughout the drying and wetting cycles are represented by hysteresis. The hysteresis phenomenon refers to the different paths the boundaries drying and wetting curves of the SWCC follows during drying and wetting process of a soil, where the drying curve always shows higher water content more than the wetting curve, at the same suction. The wetting curve is more important for practical applications than the drying curve in geotechnical engineering because structural failures, particularly in soils with dual porosity (bimodal soils), typically occur during the wetting phase. However, because measuring SWCC during wetting is expensive, time-consuming, and challenging, the wetting curve has frequently been ignored. Despite the importance of the wetting curve in practical applications and the availability of gap-graded soil in many places across the world, before this work there is no mathematical model developed to predict the SWCC during the wetting process to solve the mentioned measurement challenges. Therefore, analyses and designs are mostly conducted using only the drying curve, entirely ignoring the SWCC hysteresis. But analyses based on the drying curve alone do not accurately represent actual soil conditions, potentially leading to flawed designs and structural failures. This study introduced a new mathematical model for estimating the wetting soil-water characteristic curve (SWCC) in bimodal soils. The model uses parameters with clear physical meaning tied to wetting-SWCC related variables, making it highly useful for practical engineering applications and numerical simulations. To validate the model, hysteretic SWCCs for multiple soil types were measured in the laboratory. In addition, an alternative equation was developed to fit discrete SWCC data obtained in the laboratory. Model performance was assessed using the coefficient of determination (R²) and the Root Mean Square Error (RMSE). The results demonstrated excellent accuracy, with an average R² of 0.9945 and an average RMSE of 0.0263 across all soil samples. Given the critical influence of moisture-induced failures in geotechnical engineering, the proposed models provide valuable tools for improving analysis and design. To highlight the importance of using actual soil properties and moisture conditions, numerical slope stability analyses were equally conducted for three scenarios: using only drying curves, only wetting curves, and full SWCC hysteresis. The results show that simulations incorporating full hysteresis more closely reflect real field conditions involving cyclic wetting and drying.