Hasil untuk "Fuel"

Katsuhiro Ueno, Kazuki Ouchi, Masayuki Watanabe

Depleted uranium is a byproduct of the production of nuclear fuel, and various efforts have been made to develop new applications of it. The utilization of depleted uranium as an active material in redox-flow batteries is one of the promising applications. Quite recently we demonstrated a new static battery system using uranium and iron as active materials (UFe battery), but the potential performance is poorly understood. It is because the focus was on whether uranium works as an active material. Besides, there was limited information about the electrode reactions and the electrical conductivity of the electrolytic solutions. To clarify the ideal performance of the UFe battery, we investigated redox behaviors of uranium (IV) chloride and iron (II) chloride in chloride-containing non-aqueous solution by cyclic voltammetry and chronoamperometry techniques. In addition, the electrical conductivity of the solution was estimated by electrochemical impedance spectroscopy. As a result, the standard rate constants of both U(IV)/U(III) and Fe(III)/Fe(II) redox reactions were comparable to those in all-vanadium redox flow batteries (VRFBs), whereas the conductivity of the electrolytic solution was about 10 times lower than that of conventional aqueous batteries. The simulation using these electrochemical parameters suggested that the ideal performance of the UFe battery may be comparable to that of VRFBs when the distance between electrodes is sufficiently reduced. While there are many challenges for the application to the flow battery system, the UFe battery has the potential to be a new energy storage system and to utilize large amounts of depleted uranium.

Zhenyu Wang, Jing Sun, Zixiao Guo et al.

Vanadium redox flow batteries (VRFBs) face a significant challenge during high-temperature operation, as the precipitation of V2O5 on the positive side obstructs electrolyte flow, drastically diminishes battery capacity, and eventually leads to battery failure. While various additives have been explored to mitigate V2O5 precipitation, it continues to occur at temperatures exceeding 40 ℃. Unfortunately, there is a lack of research focused on effective methods for removing V2O5 from the battery system. The conventional approach requires disassembling the battery stacks to eliminate V2O5, a process that is not only labor-intensive and costly but also risks damaging the performance and components of the battery. In this study, we introduce an additive free strategy that enables the removal of V2O5 from the battery without the need for disassembly, thereby fully restoring battery capacity. This method is both efficient and simple, offering a cost-effective solution for V₂O₅ dissolution while potentially simplifying VRFB electrolyte manufacturing.

Marta Barros-Reguera, Esteban Lopez-Tavera, Gabriela C. Schröder et al.

Abstract Unspecific peroxygenases (UPOs) are versatile enzymes capable of oxidizing a broad range of substrates, using hydrogen peroxide as the sole co-substrate. In this study, UPOs were evaluated for their potential in the selective oxyfunctionalization of the phenolic lignin monomer 4-propylguaiacol (4-PG) to generate versatile scaffolds for the synthesis of high-value compounds. In addition to the desired peroxygenase reaction, the phenolic group of 4-PG is susceptible to undesirable one-electron oxidation (peroxidase activity). Assessment of the activity of 19 UPOs from phylogenetically diverse clades toward 4-PG revealed that several UPOs could serve as potential biocatalysts for the functionalization of 4-PG, with some enzymes showing both promising conversion yields (>50%) and regioselectivity for the peroxygenase reaction. Pronounced differences in peroxygenase:peroxidase activity ratios and regioselectivity were observed. Comparative analysis—supported by experimental activity profiles and structural data—suggest that a more constrained active-site topology contributes to the peroxygenase activity. UPOs from a clade within the Ascomycota phylum with high peroxygenase activity possess a unique aliphatic pocket in their catalytic centers. Our study provides valuable insights into the structure–function relationships underpinning enhanced peroxygenase activity of UPOs and provides a functional mapping of a broad UPO-sequence space for 4-PG, highlighting these enzymes as promising catalysts for the selective oxyfunctionalization of a phenolic lignin monomer.

Imtiyaz Hussain, Uzair Sajjad, Naseem Abbas et al.

This study addresses the durability and performance challenges in Proton Exchange Membrane Fuel Cell (PEMFC) technology, primarily focusing on optimal humidity management. Acknowledging that, beyond technical aspects, the broader commercialization of PEMFCs is critically influenced by factors such as the cost and availability of hydrogen, this research aims to provide a comprehensive solution to enhance PEMFC applicability. Utilizing Nafion (NR-212), reverse osmosis (RO), and pervaporation (PV) membranes, the study optimizes five key performance metrics: pressure drop (∆P), dew point approach temperature (DPAT), water recovery ratio (WRR), Water Flux (J), and coefficient of performance (COP). These optimizations are conducted considering variables like temperature, humidity, flowrate, and membrane material. A deep neural network (DNN) model, incorporating Bayesian surrogacy with Gaussian process, gradient boost regression trees, and random forest, is developed using experimental data. With a correlation coefficient of 0.986, the model demonstrates high accuracy in predicting performance metrics, subsequently guiding genetic algorithms for effective PEMFC humidity control. The results show significant improvements in all metrics, with optimal values achieved for NR-212, RO, and PV membranes. This study thus presents a novel, practical deep learning approach, considering both technological advancements and external economic factors, for enhancing PEMFC operations.

Jure Penga, Tino Vidović, Gojmir Radica et al.

As marine traffic is contributing to pollution, and most vessels have predictable routes with repetitive load profiles, to reduce their impact on environment, hybrid systems with proton exchange membrane fuel cells (PEMFC-s) and battery pack are a promising replacement. For this purpose, the new approach takes into consideration an alternative to diesel propulsion with the additional benefit of carbon neutrality and increase of system efficiency. Additionally, in the developed numerical model, control of the PEMFC–battery hybrid energy system with balance of plant is incorporated with repowering existing vessels that have two diesel engines with 300 kWe. The goal of this paper is to develop a numerical model that analyzes and determines an equivalent hybrid ship propulsion system for a known traveling route. The developed numerical model consists of an interconnected system with the PEMFC stack and a battery pack as power sources. The numerical model was developed and optimized to meet the minimal required power demand for a successful route, which has variable loads and sees ships sail daily six times along the same route—in total 54 nautical miles. The results showed that the equivalent hybrid power system consists of a 300 kWe PEMFC stack and battery pack with 424 kWh battery and state of charge varying between 20 and 87%. To power this new hybrid power system, a hydrogen tank of 7200 L holding 284.7 kg at pressure of 700 bar is required, compared to previous system that consumed 1524 kg of diesel and generated 4886 kg of CO₂.

Hafizah Ilma, Khairil Anwar Notodiputro, Bagus Sartono

Random forest is one of the most popular ensemble methods and has many advantages. However, random forest is a "black-box" model, so the model is difficult to interpret. This study discusses the interpretation of random forest with association rules technique using rules extracted from each decision tree in the random forest model. This analysis involves simulation and empirical data, to determine the factors that affect the poverty status of households in Tasikmalaya. The empirical data was sourced from Badan Pusat Statistik (BPS), the National Socio-Economic Survey (SUSENAS) data for West Java Province in 2019.  The results obtained are based on simulation data, the association rules technique can extract the set of rules that characterize the target variable. The application of interpretable random forest to empirical data shows that the rules that most distinguish the poverty status of households in Tasikmalaya are house wall materials and the main source of drinking water, house wall materials and cooking fuel, as well as house wall materials and motorcycle ownership.

Ana P. Abreu, Rodrigo Martins, João Nunes

<i>Chlorella</i> sp. and <i>Spirulina</i> (<i>Arthrospira</i>) sp. account for over 90% of the global microalgal biomass production and represent one of the most promising aquiculture bioeconomy systems. These microorganisms have been widely recognized for their nutritional and therapeutic properties; therefore, a significant growth of their market is expected, especially in the nutraceutical, food, and beverage segments. However, recent advancements in biotechnology and environmental science have led to the emergence of new applications for these microorganisms. This paper aims to explore these innovative applications, while shedding light on their roles in sustainable development, health, and industry. From this state-of-the art review, it was possible to give an in-depth outlook on the environmental sustainability of <i>Chlorella</i> sp. and <i>Spirulina</i> (<i>Arthrospira</i>) sp. For instance, there have been a variety of studies reported on the use of these two microorganisms for wastewater treatment and biofuel production, contributing to climate change mitigation efforts. Moreover, in the health sector, the richness of these microalgae in photosynthetic pigments and bioactive compounds, along with their oxygen-releasing capacity, are being harnessed in the development of new drugs, wound-healing dressings, photosensitizers for photodynamic therapy, tissue engineering, and anticancer treatments. Furthermore, in the industrial sector, <i>Chlorella</i> sp. and <i>Spirulina</i> (<i>Arthrospira</i>) sp. are being used in the production of biopolymers, fuel cells, and photovoltaic technologies. These innovative applications might bring different outlets for microalgae valorization, enhancing their potential, since the microalgae sector presents issues such as the high production costs. Thus, further research is highly needed to fully explore their benefits and potential applications in various sectors.

Michael O. Asare, Michal Hejcman

Abstract Wood ashes obtained from household heating and cooking are often applied to home gardens and arable fields by farmers. The effect of tree species and their locations on the elemental composition of wood ashes derived from domestic cooking and heating is unknown. The study aimed to discover the fertilizer values of wood ashes obtained from Betula pendula, Carpinus betulus, Fagus sylvatica, Larix decidua, Picea abies, Pinus sylvestris, Quercus robur, and Tilia cordata from two different localities, Hlinsko and Mšec, Czech Republic. The total element content in the ashes of dry wood samples (wood and bark) burnt at 460°C with a wood stove interfaced with a thermometer was determined using portable x‐ray spectrometry. The content (in g kg−1) of P (3.23–20.53), K (26.79–136.22), Ca (94.89–295.56), and S (2.97–11.75) in the ashes varies according to the tree species, locality, parent rock, and anthropogenic activities in the location of trees. Additionally, trace element contents ranged from 0.63–32.07 g Mn kg−1, 0.34–4.6 g Fe kg−1, 32.4–2062 mg Zn kg−1, 47.61–193.09 mg Cu kg−1, 3.99–21.53 mg Mo kg−1, and 1.50–6.62 mg Se kg−1. The pH of the ashes ranged from 8.71 to 11.54, suitable to alleviate soil acidity and a condition satisfying soil additive. A significant positive correlation between the contents of Cu, Sr, and Pb with the ashes of Picea abies, Larix decidua, Pinus sylvestris, and Betula pendula at Hlinsko is indicative of ancient anthropogenic activities input in the soil. The combustion of wood under home heating temperatures resulted in the concentration of most risk metal(loid)s, below permissible limits in agricultural soils. Application of wood ashes on arable fields requires considerable caution due to potentially toxic elements (Zn and Pb).

A.S. Plotnikova

The article is devoted to the review of various methodological approaches to the estimation of natural fire danger (NFD), as well as to the creation, updation and application of the NFD maps, which are offered by modern Russian scholars. The scale of natural fire danger assessment recommended for use and developed by I. S. Melekhov is presented and analyzed. The methodological drawbacks of this scale as stated by modern researchers are indicated. The paper reviews the development of a new methodological approach to compilation of regional scales for assessing the natural fire danger of forests, by taking into account the links between forest growth conditions as well as seasonal and climatic conditions in the regions of the Russian Federation. The method for mapping of natural fire danger on the basis of maps of plant combustible materials, proposed by the scientific group of the V. N. Sukachev Institute of Forest SB RAS, is studied. We consider studies of the Mytischi Branch of Bauman Moscow State Technical University related to investigation if the possibility for applying mathematical modeling methods for long-term forecasting of changes in NFD under different scenarios of forest management. The method for annual mapping of NFD classes, proposed in the CEPF RAS, is presented. An example of the use of NFD maps in assessing the probability of forest fires in the ICARP FEB RAS is considered. Future research areas are identified, namely, a cartographic representation of the created regional scales of NFD and the results of mathematical modeling of long-term changes in NFD.

Nurcholish Arifin Handoyono, Ali Mahmud

Penelitian bertujuan untuk mengetahui kelayakan dan keefektifan media pembelajaran berbasis android dalam proses pembelajaran. Jenis penelitian adalah R&D dengan model 4D. Subjek penelitian yaitu siswa kelas XI Teknik Kendaraan Ringan di SMK Perindustrian Yogyakarta yang terdiri dari 30 siswa. Teknik analisis data menggunakan uji N gain. Hasil penelitian menunjukan bahwa hasil validasi oleh ahli media mendapatkan nilai rata-rata presentase 83,74%, dari ahli materi dari dosen mendapatkan nilai rata-rata presentase 93,1%, ahli materi dari guru mendapatkan nilai rata-rata persentase 92,67%, uji coba kelompok kecil dengan jumlah responden 10 siswa diperoleh nilai rata-rata presentase 81,77%, uji coba kelompok besar dengan jumlah respoden 30 siswa mendapatkan nilai rata-rata persentase 84,4%, sehingga seluruhnya mendapatkan penilaian “sangat baik” dan Media pembelajaran ini efektif diterapkan dalam pembelajaran.

de Lima Silva Paulo H., Naccache Mônica F., de Souza Mendes Paulo R. et al.

One of the main issues in the area of drilling and production in deep and ultra-deep water in the oil industry is the formation of natural gas hydrates. Hydrates are crystalline structures resembling ice, which are usually formed in conditions of high pressure and low temperature. Once these structures are formed, they can grow and agglomerate, forming plugs that can eventually completely or partially block the production lines, causing huge financial losses. To predict flow behavior of these fluids inside the production lines, it is necessary to understand their mechanical behavior. This work analyzes the rheological behavior of hydrates slurries formed by a mixture of water and Tetrahydrofuran (THF) under high pressure and low temperature conditions, close to the ones found in deep water oil exploration. The THF hydrates form similar structures as the hydrates originally formed in the water-in-oil emulsions in the presence of natural gas, at extreme conditions of high pressure and low temperature. The experiments revealed some important issues that need to be taken into account in the rheological measurements. The results obtained show that the hydrate slurry viscosity increases with pressure. Oscillatory tests showed that elasticity and yield stress also increase with pressure.

闻福岳, 卢昭禹, 曹均正 et al.

柔性直流输电换流阀所用的核心器件绝缘栅双极型晶体管（IGBT）的开关速度很快，IGBT开关过程中会产生强烈的电磁骚扰，加上雷击等瞬态骚扰，导致阀厅形成非常规的强电磁骚扰环境。子模块控制器作为子模块的控制和保护单元，属于低压信号设备，位于高压端子模块本体上，负责接收阀基控制器的开关指令和子模块本体的控制保护，因此电磁兼容（EMC）性能面临着严峻考验。为提升换流阀子模块控制器的EMC能力，对换流阀子模块周围电磁环境进行了仿真分析，并根据分析结果和相关标准，设定了控制器相关EMC试验参数，对控制器进行了针对性的电磁骚扰试验考核。系统分析并优化电路和试验方法，顺利通过浪涌抗扰度试验和射频场感应的传导骚扰抗扰度试验，并在实际工程应用中得到了验证。

Wanbin Tan, Pengcheng Long, Guangyao Sun et al.

Jozef Stefan Institute (JSI), TRIGA Mark II reactor employs the homogeneous mixture of uranium and zirconium hydride fuel type. Since its upgrade, a series of fresh fuel steady state experimental benchmarks have been conducted. The benchmark results have provided data for testing computational neutronics codes which are important for reactor design and safety analysis. In this work, we investigated the JSI TRIGA Mark II reactor neutronics characteristics: the effective multiplication factor and two safety parameters, namely the control rod worth and the fuel temperature reactivity coefficient using SuperMC. The modeling and real-time cross section generation methods of SuperMC were evaluated in the investigation. The calculation analysis indicated the following: the effective multiplication factor was influenced by the different cross section data libraries; the control rod worth evaluation was better with Monte Carlo codes; the experimental fuel temperature reactivity coefficient was smaller than calculated results due to change in water temperature. All the results were in good agreement with the experimental values. Hence, SuperMC could be used for the designing and benchmarking of other TRIGA Mark II reactors. Keywords: TRIGA Mark II, Effective multiplication factor, Control rod worth, Fuel temperature reactivity coefficient, SuperMC

Renata Toczyłowska-Mamińska, Karolina Szymona, Patryk Król et al.

The abundance of cellulosic wastes make them attractive source of energy for producing electricity in microbial fuel cells (MFCs). However, electricity production from cellulose requires obligate anaerobes that can degrade cellulose and transfer electrons to the electrode (exoelectrogens), and thus most previous MFC studies have been conducted using two-chamber systems to avoid oxygen contamination of the anode. Single-chamber, air-cathode MFCs typically produce higher power densities than aqueous catholyte MFCs and avoid energy input for the cathodic reaction. To better understand the bacterial communities that evolve in single-chamber air-cathode MFCs fed cellulose, we examined the changes in the bacterial consortium in an MFC fed cellulose over time. The most predominant bacteria shown to be capable electron generation was Firmicutes, with the fermenters decomposing cellulose Bacteroidetes. The main genera developed after extended operation of the cellulose-fed MFC were cellulolytic strains, fermenters and electrogens that included: Parabacteroides, Proteiniphilum, Catonella and Clostridium. These results demonstrate that different communities evolve in air-cathode MFCs fed cellulose than the previous two-chamber reactors.

S. Liersch, J. Tecklenburg, H. Rust et al.

Climate simulations are the fuel to drive hydrological models that are used to assess the impacts of climate change and variability on hydrological parameters, such as river discharges, soil moisture, and evapotranspiration. Unlike with cars, where we know which fuel the engine requires, we never know in advance what unexpected side effects might be caused by the fuel we feed our models with. Sometimes we increase the fuel's octane number (bias correction) to achieve better performance and find out that the model behaves differently but not always as was expected or desired. This study investigates the impacts of projected climate change on the hydrology of the Upper Blue Nile catchment using two model ensembles consisting of five global CMIP5 Earth system models and 10 regional climate models (CORDEX Africa). WATCH forcing data were used to calibrate an eco-hydrological model and to bias-correct both model ensembles using slightly differing approaches. On the one hand it was found that the bias correction methods considerably improved the performance of average rainfall characteristics in the reference period (1970–1999) in most of the cases. This also holds true for non-extreme discharge conditions between <i>Q</i>₂₀ and <i>Q</i>₈₀. On the other hand, bias-corrected simulations tend to overemphasize magnitudes of projected change signals and extremes. A general weakness of both uncorrected and bias-corrected simulations is the rather poor representation of high and low flows and their extremes, which were often deteriorated by bias correction. This inaccuracy is a crucial deficiency for regional impact studies dealing with water management issues and it is therefore important to analyse model performance and characteristics and the effect of bias correction, and eventually to exclude some climate models from the ensemble. However, the multi-model means of all ensembles project increasing average annual discharges in the Upper Blue Nile catchment and a shift in seasonal patterns, with decreasing discharges in June and July and increasing discharges from August to November.

Pankaj Chowdhury, Ghodsieh Malekshoar, Ajay K. Ray

Today, global warming and green energy are important topics of discussion for every intellectual gathering all over the world. The only sustainable solution to these problems is the use of solar energy and storing it as hydrogen fuel. Photocatalytic and photo-electrochemical water splitting and sacrificial hydrogen generation show a promise for future energy generation from renewable water and sunlight. This article mainly reviews the current research progress on photocatalytic and photo-electrochemical systems focusing on dye-sensitized overall water splitting and sacrificial hydrogen generation. An overview of significant parameters including dyes, sacrificial agents, modified photocatalysts and co-catalysts are provided. Also, the significance of statistical analysis as an effective tool for a systematic investigation of the effects of different factors and their interactions are explained. Finally, different photocatalytic reactor configurations that are currently in use for water splitting application in laboratory and large scale are discussed.

Yingjie LIU, Nobuyuki OSHIMA

In this paper we propose a new level set approach to describe not only a flame&apos;s surface but also to the flame&apos;s spatial distribution. First, we derived the mathematical formulation for a one-dimensional laminar premixed flame, where the steady flame has a finite thickness depending on the diffusion flux whose physical quantity such as temperature has a relation to index function G . Further, to investigate the relationship between the present model and Inage&apos;s model, we extracted the physical meaning from the energy equation. We also validated another important parameter, the heat reaction release rate using the modified G-equation. The analysis of the heat release term leads to the definition of local flame speed, describing the distribution in the flame thickness. We evaluated the distribution of local flame speed with scalar G based on the one-dimensional solutions of premixed flames obtained by the detailed chemical reaction GRI-Mech3.0 using CHEMKIN. For CH4/Air premixed fuel, we carried out a series of calculations with different fuel rates and inlet temperatures. Based on the linear distribution of local flame speed, the modified G-equation can again be certified as the hyperbolic tangent profile.