bluuebunny/crossref_metadata_2025 huggingface dataset:
Optimizing the fundamental eigenvalue gap of quantum graphs
Authors: Ahrami Mohammed , El Allali Zakaria , Harrell II Evans M , Kennedy James B
Published: July 2024

We study the problem of minimizing or maximizing the fundamental spectral gap of Schrödinger operators on metric graphs with either a convex potential or a ‘single-well’ potential on an appropriate specified subset. (In the case of metric trees, such a subset can be the entire graph.) In the convex case we find that the minimizing and maximizing potentials are piecewise linear with only a finite number of points of non-smoothness, but give examples showing that the optimal potentials need not be constant. This is a significant departure from the usual scenarios on intervals and domains where the constant potential is typically minimizing. In the single-well case we show that the optimal potentials are piecewise constant with a finite number of jumps, and in both cases give an explicit estimate on the number of points of non-smoothness, respectively jumps, the minimizing potential can have. Furthermore, we show that, unlike on domains, it is not generally possible to find nontrivial bounds on the fundamental gap in terms of the diameter of the graph alone, within the given classes.
Particle scattering and fusion for the Ablowitz–Ladik chain
Authors: Brollo Alberto , Spohn Herbert
Published: July 2024

The Ablowitz–Ladik (AL) chain is an integrable discretized version of the nonlinear Schrödinger equation. We report on a novel underlying Hamiltonian particle system with properties similar to the ones known for the classical Toda chain and Calogero fluid with1/sinh2pair interaction. Boundary conditions are imposed such that, both in the distant past and future, particles have a constant velocity. We establish the many-particle scattering for the AL chain and obtain properties known for generic integrable many-body systems. For a specific choice of the chain, real initial data remain real in the course of time. Then, asymptotically, particles move in pairs with a velocity-dependent size and scattering shifts are governed by the fusion rule.
Elucidating the role of Ag+, Cu2+, and Fe3+ in tuning the electrical characteristics of polyaniline prepared through post-doping method
Authors: Lee J S , Yeap S P , Wang F , Cheok C Y , Ang C K , Jawad Z A
Published: July 2024

Conducting polymers possess inherent electrical conductivity, attracting significant attention in engineering applications, including dye-sensitized solar cells, gas sensors, and energy storage electrodes. Of various conducting polymers, Polyaniline has gained much attention due to its low cost of monomer, ease of bulk synthesis, high flexibility, and good environmental stability. Nevertheless, the conductivity of polyaniline is rather low when it is prepared under an un-doped state. Despite that, there is no clear information regarding how the valency of a metal dopant and its concentration can affect the electrical characteristics and other physicochemical properties of doped polyaniline. This study aims to fill this research gap by elucidating the changes in the electrical characteristics of polyaniline through metal doping. Polyaniline was synthesized through chemical oxidative polymerization in an HCl medium, followed by a post-doping to produce metal-codoped polyaniline. Three dopant materials, namely AgNO3, Cu(NO3)2, and Fe(NO3)3, were used in this synthesis, representing mono-, di-, and tri-valent metal ions, respectively. Results showed that bare PANI (which was doped with HCl only) exhibited a higher electrical conductance value of 8.44 x 10-7 S, while 1 M of Ag-codoped polyaniline, 1 M of Cu-codoped polyaniline, and 1 M of Fe-codoped polyaniline exhibited electrical conductance values of 1.73 x 10-7 S, 4.27 x 10-8 S, and 2.33 x 10-6 S, respectively. Apparently, the trivalent metal dopant was able to improve the conductivity of polyaniline; however, a detrimental effect resulted when the concentration of Fe3+ was increased to 1.5 M (overdose), resulting in a drop in electrical conductance to 4.66 x 10-8 S. In terms of morphological property, Ag-doped polyaniline exhibited a mixture of plate-like and globule-like structures, while both Cu-doped polyaniline and Fe-doped polyaniline predominantly displayed tiny globule-like structures, likely attributed to the stronger acidity of the Cu(NO3)2 and Fe(NO3)3 solutions. Meanwhile, the presence of several common bands of polyaniline such as N-H, C=N, C-H aromatic, quinoid and benzoid units are detected in the produced samples. The project outcomes are expected to guide tailored development of metal-doped polyaniline for specific electrical applications.
Evaluation of LM 43.8P blade performance at different hub height wind speeds using blade element momentum theory
Authors: Augusto G L , Chen W H , Gan Lim L A
Published: July 2024

An investigation was conducted on a three-bladed rotor similar to AVANTIS AV908. The rotor blade is appropriate for a Class I wind turbine generator and consists of three LM 43.8P blades. The 2.5 MW gearless wind turbine generator has a rated rotational speed of 16 rpm. An analysis of the LM 43.8P blade’s aerodynamics was carried out using the Blade Element Momentum (BEM) Theory to assess the turbine’s performance at different hub height wind speeds. The study employed three BEM models, including the original BEM concept without correction factors, the BEM Theory by DNV/Ris0, and the BEM Theory obtained from GH Bladed. The rotor radius is 45.1 m, and the blade comprises five different airfoils with a design tip speed ratio of 7.557. The axial and tangential induction factors, lift and drag coefficients, aerodynamic forces, and torque profiles as a function of the nondimensional rotor blade were calculated and compared with the numerical solutions obtained from the BEM models at varying upstream wind speeds. The calculation results revealed that with the original BEM concept, the axial induction factor for this particular blade became larger than 0.5 when the upstream wind speed was less than 7.45 m/s. This suggests that the Momentum Theory becomes invalid for lower wind speeds. However, the thrust force, driving force, and torque may be considerably over-predicted with hub height wind speeds larger than 9.50 m/s. It was found that out of the three models considered, the GH Bladed BEM model bears a striking resemblance with the actual power curve of AV908 with a confidence level above 95%, as indicated by a correlation coefficient of 0.99915 and a t-value of 0.51606 using Student’s t-test, implying that the two power curves have no significant difference.
A pseudo-2-dimensional model of the nonlinear impedance response of a nickel-iron battery
Authors: Abarro J M E , Paraggua J A
Published: July 2024

Pseudo-2-dimensional (P2D) models are computationally efficient tools for accurately predicting the battery’s performance. These models have been widely used to simulate lithium-ion batteries, but their application can be extended to other battery chemistries. Nickel-iron batteries are one type of storage that is regaining attention due to their durability and large theoretical specific capacity. However, their tendency to form an irreversible passivation layer and hydrogen gas leads to lower overall specific capacity and charging efficiency. Physics-based models of impedance spectra can help understand and interpret mass transport, thermodynamic, and reaction processes in a system. Batteries, being nonlinear systems in nature, can be better evaluated through nonlinear electrochemical impedance spectroscopy (NLEIS), an extension of the traditional electrochemical impedance spectroscopy (EIS), to break the degeneracy of a linear model. Base case parameters were used to generate the impedance spectra by applying moderate-amplitude current modulations. This work compared the first harmonic linear response and the second harmonic nonlinear response simulated through a P2D model. Unlike EIS, the nonlinear response shows sensitivity to charge transfer symmetry. At the negative electrode, the nonlinear response demonstrates strong dependence on the kinetic properties, suggesting that the overall battery performance is mainly influenced by the processes at the negative electrode-electrolyte interface.
Novel resistance control scheme for mitigating current sharing mismatches in parallel dual active bridge converters for DC fast charging stations
Authors: Phuc L.H. , Duc P.M. , Nhuan L.A. , Ly T.T. , Hung N.D.
Published: July 2024

Dual Active Bridge (DAB) converters have gained popularity in electric vehicle charging stations due to their high efficiency and electrical isolation. As the demand for high-powered devices and large-capacity energy storage systems grows, charging systems that integrate multiple interconnected DAB modules are emerging as a promising solution. However, prolonged operation of these modules at high power levels can cause parameter deviations from the initial DAB circuit, resulting in power variations between modules. To overcome parameter deviations, this study presents an enhanced power control approach based on output resistance adjustment, intending to achieve consistent output capacity for multiple DAB modules. In the proposed enhanced power control method, the output resistance of the DAB module is considered to be controllable, and the current-sharing mismatches among DAB modules are fed back to tune the converter output resistance for mitigating current mismatches between modules. Thanks to the proposed control method, each DAB module can operate autonomously and balance the charging current between modules. When one DAB module is suddenly cut out of the system, the other DAB modules still maintain their stability with fully guaranteed load capacity. To demonstrate the feasibility of the enhanced control approach, the small signal model of the DAB system with three modules is derived together with its frequency-amplitude diagram. Then, the effect of virtual resistance on current balancing is comprehensively tested, and the proper control signal with virtual resistance is added to the DAB voltage control loop. The simulation results have demonstrated the reliability of the proposed control method with the ability to balance the charging current between modules and stabilize the system when a single DAB module fails.
Performance of tube heat pipe solar collector with phase change material for seawater desalination system
Authors: Kusumadewi R.A. , Putra N. , Moersidik S.S. , Laksono S. , Putra G.J.P. , Utomo A.J.P.
Published: July 2024

Unlimited seawater resources resulted for utilization of desalination systems using seawater treatment process emerges as a promising technology for addressing the continually escalating need for freshwater. At present, the most notable desalination processes that are reverse osmosis, membrane distillation, multistage desalination, multiple-effect distillation, and electrodialysis, require energy generated by fossil fuels to obtain fresh water. Among the noteworthy sources of renewable energy, solar energy stands out with its manifold applications. The use of solar energy has strong advantages, such as a low maintenance and operation costs. In this study, a novel solar desalination system is introduced, which integrates tube heat pipe solar collector (THP-SC) equipped with phase change material (PCM). The aim of this research is to evaluate the performance of THP-SC equipped with PCM and without PCM. The feedwater sample used is water. Parameters measured for 24 hours were temperature, solar radiation, ambient air temperature, relative humidity, and wind speed. The greatest recorded solar radiation at noon (11.52 a.m.) is 900 W/m2 while the maximum recorded ambient temperature at 12.45 p.m. is 35.2°C. The experimental study showed that from morning to afternoon (06.00-15.00), the temperature of the evaporator section of the heat pipe on the THP-SC without PCM (46.70-56.21°C) was higher than the temperature of the evaporator section of the heat pipe on the THP-SC with PCM (33.18-44.43°C). This is because solar radiation will heat the PCM first before heating the heat pipe. PCM can store heat energy and release it at night. This can be seen from the water temperature in THP-SC with PCM (28.39-36.03) which is higher than the water temperature in THP-SC without PCM (27.17-34.01) at night, but the temperature difference is not significant. This can be caused by the large amount of heat lost to the environment in THP-SC with PCM, it is best to coat the heat pipe tube with insulation and create a vacuum to reduce heat loss.
A study of the temperature distribution in the OTEC cold water pipe using a heat and mass transfer approach
Authors: Firmansyah A I , Mukhtasor  , Satrio D , Rahmawati S , Ikhwani H , Pratikto W A
Published: July 2024

The difference between sea water temperature at a depth of around 1000 m and sea water temperature at sea level is generally used as a parameter in the design of Ocean Thermal Energy Conversion (OTEC). In practice, electricity generation is determined by the difference between the temperature of the cold seawater coming out of the Cold Water Pipe (CWP) and the temperature of the seawater at the surface. The temperature of cold sea water increases due to heat transfer experienced by cold sea water flowing through the CWP, which comes into contact with surrounding sea water which has a higher temperature. This in turn provides a lower actual temperature difference, and therefore reduces the design power capacity. However, many previous studies did not consider these lower temperature differences. This may be acceptable for cases with practically small heat transfer such as CWP with low thermal conductivity combined with good insulation used in 1000 m CWP vertical floating systems. Unfortunately, this may not be the case for many of OTEC’s proposed alternative sites, which are located on land systems that require CWP lengths of five km or more. This raises the need for careful investigation to determine the temperature of the sea water coming out of the CWP, where it is necessary to calculate the temperature distribution of the cold sea water flowing through the CWP. This paper aims to estimate the temperature distribution of cold sea water flowing through the CWP and the increase in temperature of cold sea water leaving the CWP. Analysis based on the principles of mass and heat transfer was carried out in this research, where modelling was carried out numerically using a finite volume approach. For the case considered, the change in sea water temperature at CWP from depth to the surface occurs 1-3°C, which is the accumulation of each change in sea water depth. The results of this research illustrate that designing an OTEC system with a long CWP must consider the temperature distribution of cold sea water flowing through the CWP to produce a more realistic design.
Renewable energy sharing based on the effect of energy supply from energy transportation and storage side on building load demand
Authors: Wan T C , Pan S , Wang X R , Cui Y , Yuan Y D , Wang H Y , Ge Q , Liu J L
Published: July 2024

To lower environmental-based operation costs, many literatures studied the relationship between the energy generation side (EGS) and building load (BL) demand side based on solar-based integrated energy systems (SIESs), without directly considering the effect of energy from energy transportation and storage side (ETSS) on BL demand, which may result in waste of solar energy extracted. To enhance energy utilization, this study proposed an analysis method that renewable energy source shares among different buildings was investigated based on the supply relationship between energy from the ETSS side and BL demand side. ETSS included an electric boiler/chiller (EB/C), double-effect absorption heat pump (AHP) and tank. According to the energy sources from ETSS and building loads for a hotel, a residence and a hospital on a heating/cooling day. The proposed analysis method was used to develop the potential of available renewable energy through energy sharing from the perspective of the energy consumption differences of the three buildings. The results presented that the potential of renewable energy utilization was further developed by reasonably operating the use and storage of energy sources from ETSS based on the optimization between energy sources from EGS and building loads. Energy source shares among different buildings with different energy consumption characteristics enhanced energy efficiency according to reasonably change the useable time of energy sources from tanks. When a building required a large number of energy sources, the buildings with low energy consumption directly shared renewable energy without considering the use of energy storage. This study can provide a reference for optimizing the design of integrated energy system (IES)-based architecture with different building loads.
A method for fast and accurate prediction of wind turbine thrust coefficients using classical momentum theory and power curve
Authors: Tai Vin Cent , Tan Yong Chai , Moey Lip Kean , Abd Rahman Nor Faiza , Baglee David , Saw Lip Huat
Published: July 2024

The planning and development of windfarms require accurate prediction of the thrust coefficient (cT
) of wind turbines, which significantly affects the downstream wake. Traditional methods, such as blade element momentum theory (BEMT), often necessitate detailed geometric information of wind turbines for cT
computation, information that is not frequently available, especially in the early stages of windfarm planning. This paper aims to address this challenge by presenting a novel and efficient approach to predict cT
for horizontal-axis wind turbines (HAWTs). The proposed method integrates classical momentum theory with power curve data to estimate the average axial induction factor (a), thereby enabling the calculation of cT
without requiring detailed geometric information of HAWTs. The method was validated against thirty-five existing pitch-controlled HAWTs, with R2 values ranging from 0.9604 to 0.9989. This validation confirms the accuracy of the method, making it a viable alternative to traditional techniques that demand comprehensive wind turbine geometric details. The method has demonstrated both rapidity and precision in cT
computation for turbine wake analysis, ensuring high levels of prediction accuracy and potentially lowering the barrier to entry for windfarm development. Unlike existing models predominantly focused on wind turbine power curves, cT
modelling has largely been overlooked. This study makes a unique contribution to the field by proposing a novel method for cT
prediction, thereby filling a critical gap in windfarm planning and development. However, while the study shows promising results, further research is warranted to explore its applicability in diverse windfarm scenarios and turbine configurations.
Bio-oil production from the catalytic pyrolysis of raw and torrefied corn waste by using MgO and CaO catalysts
Authors: Thu K , Fukuda S , Krerkkaiwan S
Published: July 2024

This research investigates the influence of torrefaction and catalytic pyrolysis of raw corn waste (RCW) to upgrade the quality of bio-oil. RCW was torrefied at 280°C for 16 mins to produce torrefied corn waste (TCW). Natural basic oxides (CaO and MgO) catalysts were selected because of inexpensive and high catalytic performance. Pyrolysis experiments were conducted in a bench-scaled bubbling fluidized bed reactor at 500°C. The effects of torrefaction and the presence of a catalyst on the pyrolysis product both yield and composition were investigated. The results from non-catalytic pyrolysis revealed that TCW pyrolysis gave 15 wt.% lower in oil yield, and about 6.8 wt.% lower in gas yield but the char yield was approximately 22 wt.% higher compared to the pyrolysis of RCW. Considering the effect of catalyst, the yield of bio-oil reduced slightly, while the yield of char and gas increased compared to non-catalytic pyrolysis for both RCW and TCW. The bio-oil composition derived from TCW pyrolysis contained more phenolic and aromatic compounds and significantly lower oxygenated compounds when compared to that of RCW pyrolysis. Moreover, with the presence of the catalysts, the bio-oil composition and HHVs of bio-oil was also improved.
Study of wet torrefaction and anaerobic digestion of empty fruit bunches for bioenergy production
Authors: Aziz N A M , Mohamed H , Zainal B S , Abdullah R A , Rizal N A S M , Yu K L , Jamali N S
Published: July 2024

In Malaysia, the palm oil industry generates vast amounts of solid and liquid waste, including empty fruit bunches (EFB) and palm oil mill effluent (POME). Finding efficient and environmentally friendly ways to manage and utilise this waste is crucial for sustainability. The research explores the utilisation of wet torrefaction in water for EFB, examining its impact on anaerobic digestion, specifically the dark fermentation (DF) process. The liquid product of torrefied EFB was further investigated as a substrate for biohydrogen production, employing innovative pre-treatment methods such as heat and acid on POME as the inoculum. This study focused on exploring the impact of temperature and holding time on the wet torrefaction of EFB prior to the dark fermentation process. Wet torrefaction was conducted at temperatures between 180 – 210°C and EFB: water ratio of 1:20 for 10 – 30 min, resulting in a mass yield of 52 – 54% and a chemical oxygen demand (COD) of 19.7 – 25.4 g/L COD. The chosen conditions (210°C for 30 min) demonstrated the lowest COD, validating the potential of torrefied liquid EFB for biohydrogen production. Dark fermentation was carried out at 37°C for 5 days, exploring various inoculum pretreatment parameters, including heat (80°C for 1 hr) and acid treatment (HCL pH 2-4). Liquid torrefied EFB with heat treatment inoculum exhibited the highest biohydrogen yield of 5.8 Nml, a notable 18% increase compared to the control. Through optimisation of parameters and effective waste management strategies, wet torrefaction and dark fermentation of EFB and POME emerge as promising approaches for sustainable biomass utilisation and renewable energy generation.
Sustainable bio-jet fuel synthesis techniques for the aviation industry
Authors: Tan C H , Yaw C T , Koh S P , Kadirgama K , Abed A M , Majdi H S
Published: July 2024

In the near future, the aviation industry is expected to significantly increase the usage of “drop-in” bio-jet fuel as the technologies in biofuel production advances and matures. Given the high rate of growth in the aviation sector, the demand for aerial transportation of passenger and cargo is projected to increase by two-fold in the next twenty years. This will raise the global aviation fuel consumption to an estimated 22.48 quadrillion British thermal unit (BTU) by 2040. To meet these high energy demands, it is necessary to develop alternative and sustainable methods to produce jet fuel. In light of this, intense research and numerous fundings have been allocated into developing efficient production methods for bio-jet fuel. Conventional jet fuel emits a considerable amount of greenhouse gases (GHGs) when combusted, which contributes to global warming. Compared to traditional jet fuel, bio-jet fuel is a renewable energy source and regarded to emit less GHGs. Bio-jet fuel can be produced using a diverse range of both edible (food crops such as soybean, corn, and sugar cane) and inedible (such as energy crops, agricultural wastes, and lignocellulosic biomass) feedstocks. There are various promising technologies that can produce aviation biofuel, which includes oil-to-jet [hydroprocessed ester and fatty acids (HEFA)], alcohol-to-jet, sugar-to-jet [hydroprocessing of fermented sugars (HFS)], and syngas-to-jet [Fisher-Tropsch (FT)]. Compared to the other techniques, HEFA bio-jet fuel can be sold at a lower price because HEFA requires less capital investment, capital cost, and energy cost. Although FT technique require high capital investment, FT bio-jet fuel can be sold at medium price due to its matured technology. The breakeven cost of ATJ and HFS bio-jet fuel varies greatly due to the supply and cost of sugar-rich feedstocks, as well as short lifespan of enzymes. Although bio-jet fuel has the potential to replace petroleum jet fuel in the future, there are still many technological and socio-economic challenges that must be overcome. Therefore, this paper aims to highlight the current status, technological advances, and economic challenges of bio-jet fuel production for energy transition in the aviation industry.
Decision support system for urban river water quality as a source of clean water using the SMART method
Authors: MZ Yumarlin , Rahayu Sri
Published: July 2024

Rivers play an essential role as vital water sources with roles spanning sanitation, hygiene, drinking, and agriculture, particularly in rural areas. However, Kabupaten Sleman’s river water quality, including its Kabupaten Sleman region in Yogyakarta, has severely degraded due to pollution from solid and liquid sources. Chemical contaminants have rendered the water unsafe, posing health risks. The primary objective of this study is to evaluate the water quality in the rivers of Bedog and Sembung located in Kabupaten Sleman. This evaluation utilizes Water Quality Criteria from the Republic of Indonesia Government Regulations Number 82 of 2001, alongside assigned weights. The research employs a diverse range of methodologies, including in-depth literature analysis, meticulous field observation, interviews, and comprehensive water quality assessment. A Decision Support System is adeptly employed as a strategic tool to grapple with the intricate facets inherent in the issue, thereby formulating pragmatic resolutions that facilitate judicious decision-making across diverse contexts. In addressing the dimension of water quality for communities along the Bedog and Sembung rivers, the study seamlessly integrates the SMART (Simple Multi-Attribute Rating Technique) approach. SMART’s agility in steering multi-attribute decisions expedites the decision-making process. SMART’s computational outcomes yield values of 0.304 and 0.395 for the Bedog and Sembung Rivers, respectively, both falling within the 0 to 0.49 range. This collective conclusion indicates that neither river meets the criteria for clean water quality, making it unsuitable for activities like sanitation, hygiene, drinking, and agriculture. The study underscores the urgency of rectifying river water quality, particularly in urban settings, to ensure safe and sustainable water sources for communities. The seamless integration of SMART as a decision-making tool amplifies the potential for effective interventions in navigating water quality management complexities.
Mini review on circularity framework for textile waste in healthcare
Authors: Zandberga A , Gusca J , Blumberga D , Kalnins S N
Published: July 2024

The growing impact of the healthcare sector and its environmental consequences (energy-intensive processes, material consumption and waste generation) require rapid actions to be implemented widely. To meet the environmental and climate change challenges faced by the healthcare sector, this review paper discusses how circularity frameworks can be applied to medical textile waste. This review paper explores existing circularity frameworks to address the challenges resulting from textile waste in the healthcare sector. Textile waste, primarily originating from medical garments (scrubs, isolation gowns), patient apparel and bedding, surgical textiles, wound care textiles, personal protective equipment (masks, gowns and aprons), textiles for diagnostic purposes (medical imaging), and textiles for hygiene and sanitation, present an environmental impact due to their non-biodegradability and energy-intensive production processes. This paper conducts a thorough mini review of those circularity frameworks applied to healthcare textile waste along the product’s life cycle within hospitals. The review focuses on the current waste management practices of the hospitals and evaluates innovative circular economy interventions. Case studies and pilot projects that have successfully operated circularity frameworks for managing healthcare textiles waste are included in the review to provide practical insight.
Experimental soil matrix, vortex and oil skimming technology as a tertiary treatment of wastewater effluent
Authors: Tugade C. , Pescos C.J. , Caliwag C.A.L. , Centeno C.D.V. , Tan J.D.C. , Malveda Q.M.D , Olivares R.C. , Chavez R.M. , Carrillo L.
Published: July 2024

Water is a necessary resource that must be carefully managed. Hazardous chemicals are produced with increased industrial activities and contamination has been detrimental to both people and the environment. An experimental investigation was performed to evaluate the efficiency of vortex technology, soil matrices, and oil skimmer separately for combination as a tertiary wastewater treatment in the design of a phytoremediation system. The objective of the study is to evaluate the performance of each component in removing oil and grease, reducing the concentration of ammonia, nitrate, and phosphate; quality control measures for dissolved oxygen, total dissolved solids, and chemical oxygen demand. One-way ANOVA, kinetics analysis, and adoption isotherm analysis were applied to determine the significance of the parameters. Analysis of results for the oil skimmer exhibited an efficiency of 96% in removing oil and grease after 5 hours of treatment. The vortex technology results were fluctuating with percentage removal of nitrates at 11% while ammonia with an initial concentration of 5.24 mg/L was reduced to 4.12 mg/L. Phosphate decreased after treatment from an initial of 0.87 mg/L to 0.809 mg/L. The analysis of pollutant concentration in the soil matrix after a 5-day period indicated a greater efficiency compared to the vortex technology in the removal of ammonia and phosphate. The ammonia concentration decreased from 18.7 mg/L and 21.4 mg/L to <0.1 mg/L. Similarly, phosphate concentration decreased from 15.5 mg/L to 1.13 mg/L and from 32.5 mg/L to 0.948 mg/L. The research finding underscores the efficiency of the soil matrix in removing ammonia and phosphate but recommends the need for additional intervention to lower nitrate. Overall, the three technologies showed potential and greater efficiencies in mitigating wastewater streams resulting in a notable reduction in oil and pollutant concentrations.
Horizontal-flow constructed wetlands by phytoremediation using vetiver grass, common reed, and canna lily as tertiary wastewater treatment for the reduction of pollutant concentrations of ammonia, phosphates, and nitrates
Authors: Junio C J , Ontar P A , Rutaquio V J , Manlapaz J M , Braga E B , Tugade C , Pescos C J
Published: July 2024

The discharge of untreated wastewater into rivers and water bodies poses significant environmental and public health risks. High concentrations of contaminants like heavy metals and pharmaceuticals disrupt rivers, exacerbating waterborne diseases, and leading to unsafe water in the Philippines. This study proposed the use of horizontal-flow constructed wetlands as a tertiary treatment method utilizing the plants: vetiver grass, common reed, and canna lily, to reduce pollutant concentrations in wastewater. This is to ensure compliance with water quality guidelines and general effluent standards under the Class SB Category, water suitable for fishery, tourist zones, and recreational activities. The research investigated the efficiency of phytoremediation beds in removing pollutants from wastewater under fixed hydraulic retention times. The efficiency of reducing pollutants and adsorption isotherms (Freundlich and Langmuir) were calculated to analyze the results of the sampling. Phytoremediation bed 1 demonstra ted efficient ammonia removal by 64.64%. Phytoremediation bed 2 was proficient in reducing nitrates at 83.85%, while phytoremediation bed 3 effectively reduced phosphate to an average of 26.26%, achieved after a 6-hour retention time. In addition, Freundlich adsorption isotherm was observable in most parameters in phytoremediation bed 1 such as ammonia as nitrogen, TDS, COD, and DO. Phytoremediation bed 3 exhibited the same adsorption isotherm on ammonia as nitrogen. Conclusively, the phytoremediation system met the Department of Environment and Natural Resources - Updated Water Quality Guidelines and General Effluent Standard (GES) for all parameters tested.
Strength behaviour of soil blended with two waste materials-fly ash and tire crumbs with cement
Authors: Barman P , Singh B
Published: July 2024

The rapid development in the economy has led to a growing need for electricity and automobiles, leading to the production of large quantities of fly ash (FA) and discarded tires. The safe disposal of these materials has become a significant problem. FA and scrap tyre derived material has some useful properties which can be beneficially used for enhancing the engineering properties of soil. Therefore, the study investigates the combined impact of FA and scrap tire-derived material on the stress-strain-strength behaviour of a fine-grained residual lateritic soil, incorporating a cementing agent. The research involves compaction tests followed by triaxial compression tests, where FA content added at an increment of 15% starting from 20% by weight of soil. The maximum FA content used in the mix is 50% by weight of soil. Tyre crumb (TC) which is a scrap tire-derived material, is also included in the study, with TC content ranging from 5% to 10% by weight. Additionally, 2% by weight of cement is added to each soil mix as a binding agent. Specimens are compacted in accordance with specific compaction parameters and subsequently cured for duration of up to 28 days. Strength tests are then carried out on those specimens to analyse their strength behaviour. This research primarily examines the shear strength characteristics of soil blended with FA, cement, and TC, emphasizing their geotechnical performance. Addition of 5% TC increases the peak deviator stress of cemented mix having 50% FA content from 1351 kPa to 2710 kPa at 300 kPa confining pressure and 28 days curing period. The inclusion of TC to soil-FA-cement blends is noted to significantly enhance shear strength when compared to mixes without tire crumb. Also, the stress-strain behaviour of soil is significantly influenced by addition of FA and cement in the presence of TC. Therefore, there is an ample scope of utilization of soil-fly ash-cement-TC mixes in geotechnical applications.
The effect of waste tire oil and pertamina dex oil blends on compression ignition engine performance
Authors: Khairil  , Kurniawan A F , Ali M , Sofyan S E
Published: July 2024

The improper disposal of waste tires is widely recognized as a significant environmental hazard, posing risks to both human health and safety. To address this issue, an effective approach is the transformation of waste tire into an essential product, namely Waste Tire Oil (WTO). Therefore, this study aimed to investigate the influence of blending WTO and Pertamina Dex oil on the performance of compression ignition (CI) engines. The Yanmar TF 65 R diesel engine, featuring a single cylinder, 6.5 HP of power, and a net output of 2200 rpm, was used for the experiment. The analysis was performed on various compositions of WTO and Pertamina Dex oil blends. Specifically, WTO-10 which indicated the addition of 10% volume percentage of WTO to Pertamina Dex oil, WTO-20, and WTO-30, were examined. WTO-10 indicates that a 10% volume percentage of waste tire oil was added to Pertamina Dex oil. Subsequently, the power, specific fuel consumption, and thermal efficiency of the CI engine were analyzed. The results showed that the output power significantly increased with high rotation speed. It was also discovered that adding WTO to Pertamina Dex oil did not significantly reduce CI engine power at the same running speed. Furthermore, engine speeds ranging from 1500 to 1900 rpm at a lower rate indicated a decrease in specific fuel consumption as engine speed increased. In contrast, the range 2100 rpm to 2500 rpm showed an increase in specific fuel consumption, indicating a decrease in thermal efficiency by approximately 5.6%. Based on the results of this research was suggested that WTO potensial added to pertamina dex oil as a fuel for diesel engine withoud any modification.
Greenhouse gas mitigation and yield production of Thai fragrant rice cultivation under alternate wetting and drying water management
Authors: Sriphirom P , Rossopa B
Published: July 2024

Alternate wetting and drying (AWD) water management is being promoted to replace continuous flooding (CF) water regime in rice cultivation for agricultural countries, including Thailand, to achieve the net zero greenhouse gas (GHG) emissions and cope with drought. However, its adoption in different areas yielding variable results that requires the careful approaches to prevent negative impacts on rice yield, particularly the aroma of fragrant rice, along with mitigating GHG emissions, mainly methane (CH4) and nitrous oxide (N2O). This study aims to assess the impacts of AWD on CH4 and N2O emissions, productivity, water use, and soil characteristics of fragrant rice cultivation in Thailand. Khao Dawk Mali (KDML) 105 cultivar was cultivated in the wet season and Pathum Thani (PTT) 1 cultivar was planted in the dry season under CF and AWD at different dry levels of 10 cm (AWD10), 15 cm (AWD15), and 20 cm (AWD20) below the soil surface. The emissions of GHG and water use were measured throughout the study period using closed-chamber technique and water meter equipment, respectively. Rice yields and soil properties were analyzed after crop harvesting. The results showed that rice cultivation under AWD in both wet and dry seasons reduced CH4 emissions (18.4%–27.6%) but stimulated N2O emissions (11.8%–15.0%). However, its global warming potential (GWP) was lower than CF, lowered by an average of 17.7%, 26.8%, and 25.5% under the AWD10, AWD15, and AWD20, respectively. Relative to CF, unsuccessful AWD in the wet season did not change rice yield quantity and aroma (2-acetyl-1-pyrroline: 2AP) of KDML 105. Conversely, successful AWD10 and AWD15 in the dry season promoted rice grain yield and 2AP (0.27–0.33 ppm) of PTT1, while AWD20 did not alter rice yield amount but increased rice aroma (0.47 ppm). AWD can save irrigation water in the range of 12.8%–23.0% and 15.5%–18.7% in the wet and dry seasons, respectively. AWD water regime did not importantly change the soil characteristics after crop harvest. This study concludes that AWD, especially AWD15 and AWD20, has the potential to reduce GHG emissions without affecting the quantity and quality of rice yield, along with saving water.
Life cycle analysis of a network of small modular reactors
Authors: Vinoya Carlo L , Ubando Aristotle T , Culaba Alvin B
Published: July 2024

Small modular reactors are highly-touted as the next-generation nuclear reactors that can provide alternatives to baseload energy sources such as coal and gas. Lesser dependence on these energy resources may enable faster development in poorer countries. The small modular reactors’ modularity allows for faster construction times vis-à-vis large reactors. Together with this, as more of the same reactors are constructed, costs are expected to decrease with learnings made from the experience of producing the previous one. From a technological point of view, Small modular reactors are capable of generating energy at a lower cost compared to large reactors due to the lesser capital costs that arise from faster construction times. However, it is important to understand the overall environmental impact of small modular reactors when used as a network of reactors to generate energy. Life-cycle analysis is an accepted methodology to assess various environmental impacts of technology from cradle to grave. In this work, a case study of the development of a network of small modular reactors with a unique supply chain is presented. Since small modular reactors can be sited separately, and with its comparatively higher number of reactors and plants, the same network of small modular reactors has a higher carbon footprint than a single large reactor. However, this result should be carefully considered together with other criteria that affect the decision-making in the construction and development of small modular reactors or large reactors as these may outweigh marginally higher carbon footprints, such as economic, social, and political benefits.
The influence of variations in salinity levels on the biocementing process on soil improvement of liquefaction potential
Authors: Diana N. A. , Soemitro R. A. A. , Ekaputri J. J. , Satrya T. R. , Warnana D. D.
Published: July 2024

This article presents an innovative method of soil improvement cementing to increase the shearing strength of very loose sand with 10% relative density (Dr) in saline conditions. Salt in saline soils destroys the stability of stable soils. In contrast, the salt content reduces the level of homogenization of unstable soils, causes technical problems in calcareous soils, and affects their stability, especially if the salt content is more than 3.0%. The variations in salinity levels can determine the optimal percentage of salt levels in the stabilized soil. The application of biocementation to saline soil can drastically increase the shear strength of soil in soil with potential liquefaction in coastal areas due to earthquakes. Calcium carbonate deposition (MICP) in the microbial-induced biocementing process is a new method that utilizes the metabolic processes of microorganisms in this study using Bacillus sp. In the MICP process, microbes need Ca2+ ions obtained from fly ash, which can produce SiO2 and CaO to produce CaCO3 for binding between particles. Soil improvement was carried out by combining initial soil, fly ash, mycobacteria, and variations in salinity obtained from NaCl with varying percentages of 0%, 1%, 2%, and 3,4% after testing at curing times 7, 14, 21, and 28 days. The research samples from the UCS and direct shear tests showed that the shear and UC strength that were treated increased. The highest increase in shear strength was at 3,4% salinity at 28 days of 80.9°. CaCO3 production resulting from the binding between particles in the biocementing reaction can be seen from the results of SEM tests. Soil improvement using biocementing in this study resulted in an effective increase in the strength of loose sand soil in salinity condition.
Cooling performance study of a new cooling system in subway tunnel based on field measurement and CFD simulation
Authors: Wang Y L , Zhang L , Qu Y S , Meng X , Pang H , Wang H Y
Published: July 2024

Some cities’ subways were constructed early and have been in operation for a long time. A large amount of heat accumulates in the rocks around the subway tunnels, causing the phenomenon of heat accumulation. This situation leads to the inadequate cooling capability of train air-conditioning systems, which, may even cease to function under extreme conditions. Currently, few solutions are available to address this issue. Therefore, this study proposes a new cooling system in subway tunnel. Considering the dusty environment inside the tunnel, the terminal equipment mainly consists of natural convection copper tube finless heat exchangers and a self-flushing device without fans, which cool using piston wind. By comparing field measurements of two tunnels with and without the cooling system in similar locations, the results show that the air temperature in the tunnels is reduced after the cooling system is installed. The results indicate that the average temperature in the tunnels decreases from 30.93 °C to 19.80 °C, marking a reduction of 11.13 °C after the cooling system runs for 24 hours. The temperature change in the tunnel is a long-term process, and actual measurements require significant time consumption. In this study, the long-term effect is predicted using CFD simulation in tunnels. The accuracy and credibility of the CFD simulation have been confirmed through its reasonable agreement with experimental data, with the final temperature after 24 hours achieving a relative error of less than 0.26%. Through the simulation, the temperature at a depth of 10 cm inside the tunnel wall after 24 hours is determined to be 27.56 °C, indicating a reduction of 3.44 °C compared to the initial temperature of 31 °C. This study can provide a reference for other subway tunnel cooling systems and serves as a basis for CFD simulations to verify cooling effects.
Effectiveness of using hydrophobic silica aerogel and grape seed extract in creating a sunscreen formula
Authors: Francisco K M , Allam S T , Caldona A K , De Jesus M D , Lubaton N , Sandoval S , Baylon I , Tugade C
Published: July 2024

Wearing sunscreen products protects human skin from the damaging effects of ultraviolet radiation from the sun. An experimental study was conducted to evaluate the effectiveness of utilizing hydrophobic silica aerogel and grape seed extract as additional raw materials in creating a sunscreen formula. This study aims to evaluate the acceptability of the sunscreen formulation in terms of determining its sun protection factor using UV-vis spectrophotometry, ability to remain on the surface using water resistance testing, and shelf life using a stability chamber. The methodology begins with obtaining a modified hydrophobic silica aerogel classified as cosmetic grade. The sunscreen formulation has a combination of 2 wt. % of hydrophobic silica aerogel, 3 wt.% of grape seed oil, and other ingredients using thermal procedures. The results demonstrated that the addition of hydrophobic silica aerogel and grape seed extract in sunscreen formulation exhibits satisfactory UV protection attaining an SPF value of 28.17073 which indicates a medium sun protection factor according to the standardized category of SPF values. On the contrary, the sunscreen without the active ingredients has an SPF value of 4.762. Additionally, both sunscreen’s water resistance was assessed by testing a total of 60 minutes in both tap water and salt water. The findings showed that both samples of sunscreens in tap water were more resistant compared to saltwater. Furthermore, the sunscreen with hydrophobic silica aerogel and grape seed extract stayed intact and did not dissolve in tap water after a 40-minute exposure time, but it did gradually disintegrate after 20 minutes in salt water since salt water has a higher density than tap water. In stability testing of both sunscreen formulations, the results revealed that the moisture content of the sunscreen formulation with hydrophobic silica aerogel and grape seed extract does not exceed 10% which indicates a low presence of oil. Hence, it proves its stability under the controlled conditions of 40°C and 75% relative humidity examined over one (1) month since it had a high moisture content of 78.98% obtained using the gravimetric method. For the sunscreen without these ingredients, the total moisture content under the same conditions and method is 29.07%. Thus, it indicates a high presence of oil and does not attain the standard moisture content for sunscreens. Overall, the evaluated performance of adding the hydrophobic silica aerogel and grape seed extract to the sunscreen formulation ensures its efficacy regarding its SPF, water resistance, and shelf life.