College of Engineering

Theses and dissertations submitted to the College of Engineering

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Participants in health research are often given compensation and/or reimbursement as incentives to participate and cover the costs incurred in participation. This process would involve third-parties whether in auditing or disbursement and could be a concern for the participant’s privacy. Therefore, there is a need to balance between the participant’s privacy as well as the ability to verify participant identities to prevent fraud. A solution using a blockchain-based distributed ledger and zero-knowledge proofs was explored. The study used Ethereum as the blockchain-based distributed ledger platform and Zokrates for generating and verifying zero-knowledge proofs. The study showed that it is able to provide protection against replay attacks, impostor attacks, and identity linking. Additionally, due to the system’s design, collusion resistance was also guaranteed to a certain degree. We have also tested the performance of the explored solution and it is shown that, while it does not meet theoretical expectations, it is acceptable in practical usage.

Two experimental phases were conducted in this study: In the first phase, the use of a vertical tubular photobioreactor (PBR) for toluene treatment and biomass production was investigated, and in the second phase, a combined system of a moving bed biofilm reactor (MBBR) and a vertical tubular PBR was used for toluene treatment and CO2 emission control, and biomass production. In experimental phase I, the vertical tubular PBR system achieved efficient treatment of toluene with removal efficiencies (RE) up to 98%. The mass transfer test showed that an airflow rate of 1 L min-1 had a higher average RE of 97.41% ±0.52% compared to an airflow rate of 1.50 L min-1 with an average removal efficiency of 76.28% ±34.85%. The robustness test confirmed the stability of the system (RE: 98.51 ± 0.26%) in the treatment of toluene gas. In the experimental phase II, the combined system of MBBR and vertical tubular PBR for culturing bacteria and C. vulagaris, respectively, could efficiently treat toluene with a RE of up to 99.97%, and the PBR system could capture CO2 with a RE of up to 98.46%. Dairy wastewater (DWW) provided sufficient nutrients to C. vulagaris, which increase biomass to 3.88 g L-1 compared to urban wastewater (UWW). Chlorophyll-a concentration also increased to 96.65 mg L-1. The duration of feeding with toluene, either 8 h or 24 h, did not affect the performance of the combined system. However, increasing the airflow rate from 1 L min-1 to 1.5 L min-1 decreased the RE of the combined system. On the other hand, light intensity for vertical tubular PBR affected the C. vulgaris concentration and its ability to assimilate CO2. Moreover, C. vulgaris cultured with DWW accumulated a higher lipid concentration (34.50%) compared to C. vulgaris cultured with UWW, which had a lipid concentration of 9.70%. In this study, the microbial analysis was performed species-specific oligonucleotides targeting 16S rDNA to verify that the system was able to treat toluene and produce CO2. Four microorganisms were characterized, and the analysis detected three microorganisms: P. putida, B. paralicheniformis, and Brevibacillus agri.

Current oral medications for type 2 diabetes target a single main physiological mechanism. They either activate or inhibit receptors to enhance insulin sensitivity, increase insulin secretion, inhibit glucose absorption, or inhibit glucose production. In advanced stages, combination therapy may be required because of the limited efficacy of single-target drugs; however, medications are getting more costly, and there is also the risk of developing the combined side effects of each drug. Thus, identifying a multi-target drug, either plant-based or semi-synthetic, may be the best strategy to improve treatment efficacy. This study sees the potential of 3,083 Philippine phytochemicals as a source of natural inhibitors against four targets of diabetes: Protein-tyrosine phosphatase 1B (PTP1B), Dipeptidyl peptidase-4 (DPP-4), Sodium-glucose co-transporter 2 (SGLT-2), and Fructose 1,6-biphosphatase (FBPase). A wide array of computer-aided drug discovery techniques were employed to carry out the virtual screening process: ADMET profiling revealed 373 molecules with excellent bioavailability and toxicity properties; DFT optimization predicted their most accurate 3D structures; consensus docking identified the ten highest-scoring ligands per protein comparable to reference compounds' scores; molecular dynamics simulation elucidated the stability of the protein-ligand complexes trough RMSD, RMSF, and H-bond diagram analysis; and MM/PBSA energy calculations determined the binding affinity of the compounds against the four receptors and the key residues integral to binding. Through in silico methods, we have identified seven potential natural inhibitors against PTP1B, DPP-4, and FBPase, and ten against SGLT-2. Eight plants containing at least one natural inhibitor of each protein target were also identified (Eclipta prostata, Agave sisalana, Piper aduncum, Curculigo orchioides, Luffa cylindrica, Moringa oleifera, Alium cepa, and Helianthus annuus). It is recommended to investigate further the plants' potential to be transformed into a safe and scientifically validated multi-target drug to improve diabetes therapies.

In the first part of the study, phytosterols were found to primarily inhibit all four proteins. Stigmasterol and brassicasterol are potential inhibitors against PTP1B; campesterol against DPP-4; sitosterol, stigmasterol, and brassicasterol against SGLT-2; and campesterol and stigmasterol against FBPase. Since each protein is inhibited by at least one phytosterol, it is possible that a sterol or analog structure of a sterol will inhibit all four proteins. For this, we used the four phytosterols as parent compounds for creating 10,853 new sterol analogs. These analogs underwent the same virtual screening process employed in the first part of the study. Only 632 compounds with favorable ADMET properties underwent molecular docking, and the top ten ligands with the highest consolidated docking scores proceeded to the MD simulations and MM/PBSA calculations. Out of the ten candidates, eight sterol analogs demonstrated stable complex behaviors with all four protein targets and registered comparable binding affinity to the reference compounds (CID: 10905362, CID: 13831959, CID: 23724485, CID: 54307943, CID: 60030863, CID: 91041629, CID: 101306816, and CID:157570120). These semi-synthetic compounds are also recommended in the next stage of the drug discovery process to verify their viability as a multi-target drug against diabetes.

Cacao (Theobroma cacao) is one of the most important high-value crops worldwide. Its beans are used for the production of chocolates and other cocoa-based products. During processing, a large amount of waste is generated which is mainly composed of the cacao pod husks (CPHs) which accounts for 60-80% of the weight of the whole fruit. Traditionally, these CPHs are viewed as waste material and are often disposed of or left to decompose which leads to environmental concerns and lost economic opportunities. In recent years, while there are notable advances in the utilization of CPHs, there remain lots of opportunities for the development of eco-friendly and low-cost production processes that will effectively convert cacao pod husks into valuable products.

This study aims to present other potential applications of the CPH. It is divided into two parts: a.) extraction of cellulose from two varieties of CPH using conventional and microwave synthesis, and b.) microwave-assisted, acid-hydrolyzed, one-pot synthesis of levulinic acid from CPH biomass. Cellulose was successfully isolated from CPH through conventional heating and microwave heating method. Analysis of the functional groups present through FTIR, surface morphology through SEM imaging, and physicochemical properties of the product confirmed its cellulosic properties. Moreover, these properties are comparable to the commercial microcrystalline cellulose. For the investigation of the potential of readily available household items, environmentally-benign and low cost catalysts – KAl(SO4)2 and CH3COOH – were used for one-pot, microwave-assisted synthesis of levulinic acid from cacao pod husks without pretreatment. Result showed the potential of KAl(SO4)2 and CH3COOH to facilitate the production of levulinic acid from cacao pod husk. Characterization of the solid residue called humin from the synthesis revealed its macroporous structure that might be suitable for adsorption applications. Moreover, its heating value was comparable to the heating value of coal. The characterization showed that it can be a possible hydrochar for soil application or a potential material for biogas.

This study presented an environment-friendly approach to accessing cellulose from cacao pod husk through microwave-assisted extraction and the use of a greener alternative for bleach, H2O2. Moreover, this study showed the potential use of readily available and low-cost catalysts for the acid-catalyzed hydrolysis of cacao pod husk biomass to synthesize levulinic acid. The properties of the humin also showed its potential for fuel and/or hydrochar applications.

The energy crisis in the Philippines drastically affects, and is more prevalent in the countryside with rotating power interruptions. The Department of Energy has been promoting the exploration and utilization of renewable energy as an alternative energy resource to fossil fuels as mandated in the Renewable Energy Act of 2008. Hydro, wind, solar, geothermal, and biomass are more commonly used in the country due to the established and available technologies that can generate electricity from these energy sources. Another abundant renewable energy resource across the archipelago is ocean energy. As published by the National Renewable Energy Program, the first ocean power plant to generate electricity was expected to operate by 2018. However, developments for ocean energy projects are still in the pre-development stage. Funding, availability of
technology providers, COVID-19 pandemic, and actual ocean data parameters are probable causes of delayed ocean project implementation.

Scarcity of actual ocean data parameters was seen as a gap when performing ocean energy resource assessment. Hence, tidal models are used to initially identify locations of potential device deployment and its indicative power capacity based on the
Department of Energy's pre-identified ocean energy extraction sites. However, there are still several gaps that need to be studied further: (1) lack of resource assessments in terms of techno-economic and suitability viability, (2) no further assessment within the pre-identified locations of the Department of Energy, and (3) single device deployment assumption for energy generation.

This research aimed to provide results on the mentioned gaps in energy resource assessment. It focused on extracting energy from the tidal currents using a horizontal axis tidal turbine within the Regions 8 and 13, where pre-identified sites are located as its area of interest. A unique method of determining tidal velocity was proposed and implemented in this research due to the unavailability of actual tidal velocity measurements. Integration of the available data from PhilSHORE and tidal simulations successfully created a synthetic velocity profile in contrast toother studies which had used Delft3D and tidal height difference as the method to estimate the tidal velocity within a specified area of interest. The Levelized Cost of Energy was then calculated based on the synthetic velocity profile from a list of identified horizontal axis tidal turbines to assess the techno-economic feasibility of the device for a 10-unit deployment. Exclusion and suitability parameters were determined to establish the suitability of device deployment at potential sites within the area of interest, such as submarine power cable, marine protected areas, marine ecosystems & aquaculture, faults and trenches, shipping routes/navigation zone, coastal zone, bathymetry, earthquake, fishing zone, Levelized Cost of Energy, power substation distance, ship density, and tropical cyclone track. The suitability analysis is performed using a Multi-Criteria Decision Analysis, specifically the
Analytic Hierarchy Process to evaluate device viability at the specified location of deployment based on the Acceptable, Tolerable, and Geometric Mean acceptable condition metrics for different deployment categories (first, second, & commercial
arrays) as referenced from Ocean Energy Systems.

Among the list of identified tidal turbines, SeaGenS-2MW delivered significant results according to the deployment categories, with Placer substation as reference point of power grid connection. It is noted that the tolerable condition metric at commercial array deployment for suitability analysis marked the conservative conclusion, with 23 potential sites equivalent to 460 MW indicative power capacity, and 0.03 to 0.18 $/kWhr Levelized Cost of Energy values with greater than 80% normalized suitability index value. To highlight the significant locations from the 23 potential sites, 5 sites had 97% normalized suitability index value, with calculated Levelized Cost of Energy ranging 0.03 to 0.07 $/kWh located at Malimono, Surigao del Norte.