High Energy Content Research Articles

Fingerprinting Mediterranean hurricanes using pre-event thermal drops in seawater temperature

Extreme atmospheric-marine events, known as medicanes (short for “Mediterranean hurricanes”), have affected the Mediterranean basin in recent years, resulting in extensive coastal flooding and storm surges, and have occasionally been responsible for several casualties. Considering that the development mechanism of these events is similar to tropical cyclones, it is plausible that these phenomena are strongly affected by sea surface temperatures (SSTs) during their development period (winter and autumn seasons). In this study, we compared satellite data and the numerical reanalysis of SSTs from 1969 to 2023 with in situ data from dataloggers installed at different depths off the coast of southeastern Sicily as well as from data available on Argo floats on the Mediterranean basin. A spectral analysis was performed using a continuous wavelet transform (CWT) for each SST time series to highlight the changes in SSTs prior to the occurrence of Mediterranean Hurricanes as well as the energy content of the various frequencies of the SST signal. The results revealed that decreases in SST occurred prior to the formation of each Mediterranean hurricane, and that this thermal drop phenomenon was not observed in intense extra-tropical systems. The spectral analyses revealed that high CWT coefficients representing high SST energy contents were observed before the occurrence of a Mediterranean hurricane. This information may provide a useful fingerprint for distinguishing Mediterranean hurricanes from common seasonal storms at the onset of these events.

Millets: A Scientific Perspective on Their Nutritional and Health Relevance

Millets are resilient crops with the ability to endure various climatic conditions, making them sustainable and drought-resistant. Over the past few decades, their production has increased to meet the nutritional needs of the growing global population. These grains are rich in essential nutrients, including proteins, carbohydrates, fats, minerals (iron, zinc, magnesium, calcium and phosphorus), vitamins (niacin, thiamine, riboflavin, folate and vitamin E) and bioactive compounds. Millets are recognized for their high-energy content, addressing malnutrition effectively. They serve as a valuable source of medicinal and nutraceutical properties, offering antioxidants that play a role in preventing health issues such as high blood pressure, heart disease, obesity, cancer, cardiovascular diseases, and diabetes. Additionally, millets contribute to a decrease in tumour cases. Due to their nutritional composition and bioactive components, millets are considered a long-term and sustainable solution for ensuring a stable supply of food and feed materials. This review aims to emphasize the scientific aspects of millets, focusing on their nutritional content, biologically active compounds, and pharmaceutical properties.

Experimental and numerical study on dynamic response of offshore wind turbine subjected to earthquake loads

In order to investigate the response of offshore wind turbines (OWTs) under earthquake, shaking table test is conducted using a 6.45 MW OWT as prototype. The effective length of the embedded steel pile is determined using the equivalent embedment method, and a scale model with a similarity constant of 1:15 is designed. The dynamic characteristics of the scale model are evaluated through position-shift and white noise. Three earthquakes with different spectrum characteristics are utilized as inputs, and subsequently, an analysis is performed to assess the earthquake response of the OWT. The results demonstrate that the dynamic characteristics between the scale model and the prototype model meet the similarity constants. Due to the eccentric mass, torsional vibrations are induced when subjected to bidirectional excitation, resulting in the occurrence of ‘beat vibration’ phenomenon. The acceleration is significantly influenced by the excitation spectrum, with the maximum occurring at either the top or 2/3 height, and Darfield with wide spectrum result in a more pronounced stimulation. The displacements are all observed at the pinnacle of the tower. The Imperial and Kocaeli, characterized by shorter duration and higher energy concentration, elicit more pronounced displacement. Stress concentration occurs at the lower 1/3 due to sudden stiffness change.

A new perspective on obesity: perception of fat taste and its relationship with obesity.

Obesity, which results from a long-term positive energy balance, is affected by many factors, especially nutrition. The sensory properties of foods are associated with increased food intake through hedonic appetite. Taste perception, a component of flavor, is also responsible for increased consumption, through reward and hedonic mechanisms. Foods with high fat and energy content are among the foods that create the reward perception. The perception of fat taste, the primary taste that has recently entered the literature, may also be associated with increased food consumption and body weight. Therefore, in this review, the relationship between fat taste and obesity is examined, using the latest literature. Different hypotheses have been proposed regarding the mechanism of the relationship between fat-taste perception and obesity, such as hedonic appetite, microbiota, decreased taste perception, and increased taste threshold level. In addition, some studies examining this relationship reported significant associations between the level of fat-taste perception and obesity, whereas others did not find a significant difference. Considering the prevalence and contribution to obesity of Western-style nutrition, characterized by high amounts of fat and sugar consumption, elucidating this relationship may be an essential solution for preventing and treating obesity.

Relationship between intake of energy-dense diets and nutritional status of adolescents in primary schools in Nairobi City County, Kenya

Background: Energy-dense diets are of low nutrient quality but high energy content and this may have adverse health outcomes, especially in adolescence where the body is transforming from childhood to adulthood. Intake of energy-dense diets is associated with various forms of malnutrition including obesity, overweight, underweight and other micronutrient deficiencies. There is however scanty information about the relationship between the intake of energy-dense foods and adolescents' nutritional status. Aims: This study aimed to establish the relationship between intake of energy-dense diets and the nutritional status of adolescents in Nairobi County. Subjects and Methods: The study was a cross-sectional descriptive research design involving quantitative techniques of data collection. A total of 161 adolescents, 87 females and 74 male aged 10-14 years participated in the study. Cluster sampling was used to select schools in Embakasi South Sub- County. Simple random sampling was used to select adolescents in classes 5, 6 and 7. Data were collected using structured questionnaires, 7-day food frequency questionnaires, and anthropometric measurements. Data analysis was done using; SPSS version 23.0 (quantitative data), ENA for SMART (anthropometric data), Nutrisurvey software (Dietary data) and hypothesis testing (Pearson correlation). Results: The study established a burden of malnutrition among adolescents in Nairobi County (13%) underweight, (5.7%) overweight, (4.3%) severely underweight, and (2.5%) obese. The energy-dense foods which were found to have significant relationship with the nutritional status of the adolescents were: potato chips (r = 0.044, p = 0.045), doughnuts (r = -0.02, p = <0.001), pancakes (r = -0.001, p = 0.762), bhajia (r = -0.014, p = 0.897), cheese (r = -0.107, p-value = 0.660), and Regular soft drink (r = -0.147, p= 0.101. Conclusion: The nutritional status of the adolescents was influenced by the intake of some energy-dense diets and sociodemographic characteristics. Keywords: Food energy-density; dietary intake; undernutrition; overweight; obese; fatty foods.

A comprehensive review on effective parameters on microalgae productivity and carbon capture rate

Rising carbon emissions caused by population growth and industrialization is a significant environmental challenge in various countries. To combat this issue, Renewable Energy (RE) and Carbon Capture and Storage (CCS) technologies should be commercialized to reduce Greenhouse Gas (GHG) emissions and generate carbon-free energy. One such technology is the use of microalgae, which can directly capture CO2 from the air through photosynthesis and potentially produce biofuels due to their high energy content. However, the carbon capture rate of microalgae varies globally due to numerous parameters and variables affecting microalgae productivity. Additionally, microalgae productivity and carbon capture formulas yield different results worldwide, especially in outdoor industrial-scale cultivation. This research aims to comprehensively review the effective variables and parameters in carbon capture by microalgae based on microalgae productivity and carbon capture formulas. The research also ranked countries based on CO2 production in four different categories to determine whether the biggest carbon producer countries could exhibit suitable weather conditions for microalgae cultivation. Findings reveal optimal ranges of critical variables in the microalgae growth formula, including temperature, solar radiation intensity, Photon Flux Density (PFD), and sunlight duration. The study also analyzes microalgae cultivation, carbon capture, and oxygen production formula in different systems such as Open Ponds (OP), Tubular Photobioreactors (TPBR), and Flat Plate Photobioreactors (FPPBR), while discussing other influential parameters. In conclusion, emphasizing the adjustment and utilization of optimal values of effective parameters in microalgae cultivation not only holds promise for future carbon capture by microalgae but also pushes human beings toward sustainable development goals.

Comparative analysis of different heat transfer models, energy and exergy analysis for hydrogen-enriched internal combustion engine under different operation conditions

The implementation of hydrogen as a fuel in internal combustion engines is widely considered a favorable optimal due to its zero-carbon emissions and high energy content. Heat transfer from engine cylinder walls has a major role on engine combustion, performance and emission characteristics. In this study, heat transfer analysis conducted by different heat transfer models and identify the best model to analyse the energy and exergy analysis of hydrogen enriched internal combustion engine. A series of experiments were conducted on a compressed natural gas internal combustion engine across varying hydrogen fractions, EGR ratios, engine speeds and load conditions to capture in-cylinder pressure data and heat transfer rate. The authors compared six distinct models for heat transfer based on absolute percentage errors of maximum pressure and indicated mean effective pressure. These models systematically incorporated into a quasi-dimensional combustion model (QDCM) on MATLAB for hydrogen-compressed natural gas engine, accounting for diverse operating conditions. Convective heat transfer models, including Woschni, Nusselt, Hohenberg, Han, Eichelberg, and Assanis correlations were employed. Comparative analyses were undertaken to identify the most precise correlation for predicting engine in-cylinder pressure and heat transfer rates with experimental results across a broad spectrum of operational conditions. The Woschni model, as presented, is most suitable for the QDCM of the hydrogen-compressed natural gas fuel blend. This suitability is indicated by the close alignment of Taylor length and turbulent intensity coefficients to 1, as well as the minimal absolute percentage error observed for indicated mean effective pressure. It is also observed that heat transfer rate is increased by increasing the engine load 25 %, 50 %, 75 % and 100 % as 49.57 J/deg, 129.26 J/deg, 245.35 J/deg and 250.62 J/deg respectively and heat transfer rate is decreased by increasing the speed of engine 1100 rpm, 1200 rpm, 1500 rpm and 1700 rpm as 137.34 J/deg, 134.21 J/deg, 95.33 J/deg and 48.57 J/deg respectively. The energy and exergy analyses revealed that elevating the engine load corresponds to a reduction in exergy destruction. Brake energy increased 15 % by increasing the load conditions from 25 % to 100 % and decreased 7 % by increasing the speed from 1100 rpm to 1700 rpm. Another significant finding from this study is that the values of both energy and exergy efficiencies were 38.42 % and 40.12 % respectively obtained by thermodynamic analyses.

A density functional theory investigation of the substituent effect on acyclovir and guanine derivatives for applications on energetic materials

The main challenge in designing new energetic materials is to find a good balance between four seemingly incompatible requirements, namely, high-energy content, low sensitivity, low production costs and less-polluting content. Fused nitrogen heterocycles of imidazole and pyrimidine, such as acyclovir and guanine, may offer interesting features due to the combination of a coplanar framework and a large conjugate system, which contribute to a reduced sensitivity, and a number of energetic bonds that can be increased by the introduction of explosophore substituents. In this work, to evaluate the potential of acyclovir and guanine derivatives as energetic materials, density functional theory (DFT) calculations were carried out to investigate the influence of the type and position of the explosophore substituent groups –NO2, –NHNO2, –N3, –ONO2, –CN, −N=N−, and −N=N(O)− on the energetic properties and chemical reactivity of 91 acyclovir- and guanine-based molecules, including thirty one nitramines, three nitroheterocycles, seventeen azides, seventeen nitrate esters, seventeen nitriles, three azo and three azoxy compounds. Several molecular properties were computed, including the chemical reactivity, the heat of formation and the detonation velocities and pressures using semiempirical equations. Among the molecules with no bridge groups, we found that, except for cyano group, position 4 were the most stable for acyclovir derivatives, whereas, except for the azido group, position 2 and 5 provided the most stable compounds for guanine derivatives. Among the bridged derivatives, depending on the molecule and positions, the nitrate esters and the nitro derivatives were more stable. In comparison with the parent compounds, calculations showed that the heat of formation (HOF) increased the most with azido and cyano groups, the density increased substantially with nitrate esters, nitro and nitramino groups, and the detonation velocities and pressures increased the most with nitrate ester, nitro and nitramino groups. Although azo groups resulted in higher HOFs than azoxy groups, azoxy derivatives showed superior values in terms of density, heat of maximum detonation, detonation velocity and pressure. Four nitrate esters (GD134, GD245, AZOXYGD13 and AZOXYGD25) displayed higher values of detonation velocity and pressure than RDX. The designed nitramines are less sensitive to impact than RDX. Except for GD134 and GD245, all guanine-based nitrate esters, with no bridge linkages, are expected to be less sensitive to impact than TNT. Due to the combination of good performance and stability, the compounds GD25, GD13, GD45, GD34, and GD14 have considerable potential as energetic materials. Therefore, their synthesis and further investigation are recommended.

Potential and utilization of sorghum in dry land as animal feed

Sorghum (Sorghum bicolor (L.) Monch) is a cereal crop that is drought tolerant and can be produced worldwide. Sorghum plants can be developed in Indonesia as animal feed. This is due to agroecological conditions that can tolerate land conditions in Indonesia. This article aims to review the potential and utilization of sorghum as a source of animal feed that can be developed on dry land. The article method uses descriptive by reviewing the results of research on sorghum. Harvest can be done at the age of 85 to 90 days because sorghum has high nutritional value and is a substitute for other feed sources, because it has a high chemical composition, vitamin, mineral, and energy content. The nutritional content of crude protein sorghum is 10,4, fat 1,5 and ash 6,8%. In fresh conditions, the leaves and stems of sorghum do not last long, so it needs processing in the form of silage to extend its shelf life so that it can be used in the dry season. Giving feed derived from leaves, straw, by-products of sorghum shows a positive response in livestock. This study concludes that orgum has the potential to be developed as a source of animal feed because it has a fairly good nutritional content and has the potential to be developed on dry land.

Synchronous odd symmetric transform for rolling bearing fault diagnosis

Time-frequency analysis (TFA) is an important tool to process non-stationary signals and detect bearing faults. For considering energy concentration, computational efficiency, and computational accuracy, a novel TFA technique, termed synchronous odd symmetric transform (SOST) is proposed in this paper. In the SOST, the odd symmetry extraction operator (OSEO) is defined according to the odd symmetric window based short-time Fourier transform (OSTFT). The main idea of OSEO is to obtain accurate instantaneous frequency (IF) ridges in a satisfactory computation time. Meanwhile, the STFT result is retained at the IF ridges, and the time–frequency representation (TFR) with high energy concentration is calculated. The performance of the developed technique is verified by a multi-component signal with strong frequency-modulated and amplitude-modulated (FM-AM) laws. Experimental analysis results show that the proposed SOST can display bearing fault-related time–frequency trajectories with high time–frequency resolution.

Enhancing Methane Yield in Anaerobic Co-Digestion of Primary Sewage Sludge: A Comprehensive Review on Potential Additives and Strategies

Traditionally, anaerobic digestion has been applied to mixed sludge, combining primary sludge (PS) with secondary sludge. However, recent research has unveiled the advantages of dedicated PS digestion due to its higher energy content. Anaerobic digestion (AD) of primary sewage sludge can offer a sustainable solution for managing sewage sludge while generating renewable energy. The present study provides a comprehensive examination of the current state of knowledge regarding the anaerobic digestion of PS. Co-digestion of PS with organic substrates, including food waste and agro-industrial residues, emerges as a promising approach to boost biogas production. Additionally, the utilization of additives such as glucose and clay minerals has shown potential in improving methane yield. Critical factors affecting AD, such as pretreatment methods, carbon-to-nitrogen (C/N) ratio, temperature, pH, volatile fatty acids (VFAs) levels, organic loading rates (OLR), inoculum-to-substrate ratio (ISR), and the role of additives, have been meticulously studied. Finally, this review consolidates existing knowledge to advance our understanding of primary sewage sludge anaerobic digestion, fostering more efficient and sustainable practices in sludge management and renewable energy generation.

Constructing independent CNTs conductive network to boost combustion performance of metastable intermixed composites

AbstractNovel metastable intermixed composites (MICs) constructed by carbon nanomaterials are expected to achieve high energy content and high combustion efficiency, but traditional preparation technologies always bring barely improvement in performance. Herein, novel PVDF/CuO/Al@CNTs MICs with independent continuous carbon nanotubes (CNTs) conductive networks were prepared by thoroughly utilizing the conductivity and photothermal properties of CNTs. A conductive network can be constructed at the interface of each encapsulated PVDF/CuO/Al particle with the addition of >0.5 wt% CNTs. The great increase in electrical and thermal conductivity of PVDF/CuO/Al@CNTs MICs indicates excellent energy transfer efficiency across the sample. Significant enhancement of the combustion reaction has been achieved, with the minimum ignition energy and ignition delay time of PVDF/CuO/Al@CNTs3 reduced by ~31% and ~50%, respectively. This indicates that the CNTs with unique photothermal properties can be utilized as an effective igniter. Moreover, the optimal PVDF/CuO/Al@CNTs1 MICs enhanced the pressurization rate (~300%), energy output (~55%), and combustion velocity (~200%). The mechanism of the fast combustion reaction can also be discussed by the weak interface interaction and the energy conductive of the CNTs network throughout the sample. This work provides a modern strategy for strong combustion MICs that can be generalized and applied in the field of energetic materials.Highlights An independent continuous CNTs conductive network was prepared with a small amount of CNTs. The electrical and heat conversion efficiency is greatly improved. CNTs with unique photothermal properties can be utilized as an effective igniter. The laser sensitivity is improved, and the reaction energy, pressure, and pressure rates are significantly increased. The combustion performance was significantly improved, and more intense, and the combustion speed was significantly increased.

Maximizing Bio-Hydrogen and Energy Yields Obtained in a Self-Fermented Anaerobic Bioreactor by Screening of Different Sewage Sludge Pretreatment Methods

Egypt faces significant challenges in managing its sewage sludge generated in large quantities from wastewater treatment plants. This study investigates the feasibility of utilizing sewage sludge as a renewable resource for hydrogen production through anaerobic digestion at the 100 L bioreactor level. Hydrogen is considered a promising alternative energy source due to its high energy content and environmental benefits. To optimize the microbial degradation process and maximize hydrogen production from sewage sludge, a specialized pretreatment is necessary. Various pretreatment methods have been applied to the sewage sludge, individually and in combination, to study the bio-hydrogen production from sewage sludge. The four methods of treatment were studied in batch assays as a pilot scale. Thermal pretreatment of sewage sludge significantly increases bio-hydrogen production yield compared to other sewage sludge pretreatment methods, producing the highest H2 yield (6.48 LH2/g VS). In general, the hydrogen yield of any type of pretreated inoculum was significantly higher than the untreated inoculum. At the same time, alkaline pretreatment improved the hydrogen yield (1.04 LH2/g VS) more than acid pretreatment (0.74 LH2/g VS), while the hydrogen yield for the combination of pretreatments (shock alkali pretreatment) was higher than both (1.73 LH2/g VS), On the other hand, untreated sewage sludge (control) had almost no hydrogen yield (0.03 LH2/g VS). The self-fermented anaerobic bioreactor improved sewage sludge utilization, increased bioenergy yields, and seems to be promising for treating complex wastes at this scale.

Comparative Feasibility and Environmental Life Cycle Assessment of Cotton Stalks Gasification and Pyrolysis

In a circular economy, significant emphasis is given to the energetic valorization of agricultural byproducts. Cotton stalks are suitable as a feedstock for the production of bioenergy due to their high energy content. This study’s main focal areas are the economic viability and environmental implications of a system that can gasify or pyrolyze 25,500 tons of cotton stalk annually. To learn more about how gasification and pyrolysis affect the environment, a life cycle assessment (LCA) was conducted. This analysis evaluates the whole value chain and covers all stages of the cotton supply chain from cradle to gate, including production, harvest, transportation, and utilization. According to the findings, both systems exhibit economic viability, generating sizable profits and having quick payback times. However, despite its larger initial expenditure of EUR 2.74 million, the pyrolysis unit ends up being the better option because it has a payback period of 1.58 years, a return on investment (ROI) of 58% and a net present value (NPV) of EUR 21.5 million. Gasification is still an economically attractive alternative with a lower initial investment (EUR 1.81 million), despite having a lower ROI (36%) and NPV (EUR 10.52 million), as well as a longer payback period (2.41 years). However, the environmental implications of the gasification option are generally higher than those of pyrolysis. The impacts of gasification on fossil depletion (FDP) were estimated to be 5.7 million kg oil eq., compared to 5.3 million kg oil eq. for pyrolysis. Similarly, gasification resulted in 41.55 million kg U235 eq. and pyrolysis in 41.5 million kg U235 eq. related to impacts on ionizing radiation (IRP_HE). Other impact categories that emerge as the most important are freshwater eutrophication (FEP) and marine eutrophication (MEP).

Cerium-Organic Framework (CeOF) for hydrogen generation via the hydrolysis of NaBH4

Hydrogen gas has been considered an eco-friendly energy source with a high energy content, making it a suitable energy carrier for several industries. A cerium-organic framework, denoted as CeOF, was synthesized by reacting cerium with a tricarboxylic organic linker using a solvothermal method. The material's characteristics were analyzed using X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), thermogravimetric analysis (TGA), and Fourier transforms infrared spectroscopy (FT-IR) to confirm its crystallinity, phase purity, elemental composition, chemical bonding, morphology, and thermal stability. CeOF catalysized the release of hydrogen from solid hydrogen storage materials, e.g., sodium borohydride (NaBH4) by the reaction with water via hydrolysis. An examination was carried out to analyze the influence of catalyst loading, NaBH4 weight (0.2–3 wt%), and reaction temperature. The CeOF catalyst showed a significant hydrogen generation rate (HGR) of 1800 mLH2·gcat-1·min−1, with an activation energy of 58.8 kJ·mol−1. It showed good catalytic recyclability enabling continuous hydrogen production for four cycles without any significant decrease in the material’s performance.

Lithium-grafted Si-doped γ-graphyne as a reversible hydrogen storage host material.

In recent years, hydrogen (H2) has become the most sought-after sustainable energy carrier by virtue of its high energy content and carbon-free emission. The practical implementation of hydrogen as an alternative fuel calls for an efficient and secure storage medium. Within this framework, we have investigated Li-grafted Si-doped γ-graphyne for H2 storage applications by implementing the cutting-edge density functional theory (DFT). A dynamically and thermally stable Si-doped γ-graphyne (SiG) monolayer is functionalized with Li metal atoms that augmented the hydrogen binding strength of the nanolayer by almost three times, owing to the polarization effect of the Li atoms. The Li metal atoms get adsorbed over the monolayer, allowing a binding energy of -2.73 eV that is greater than the Li cohesive energy (-1.63 eV), which eliminates the metal-metal clustering probability. The reliability of the Li-functionalized SiG monolayer (Li8SiG) at elevated temperature has been further substantiated by performing and analyzing ab initio molecular dynamics (AIMD) simulations at 400 K. It is noteworthy that a total of four H2 molecules are held up by each Li atom with an average adsorption energy of -0.32 eV and a maximum gravimetric capacity of 8.48 wt%, which remarkably follows the US-DOE parameters. Partial density of states and Hirshfeld charge analysis are utilized to recognize the interaction channel which reveals the Kubas and Niu-Rao-Jena-like bonding among the metal atoms and loaded hydrogen molecules. The hydrogen occupancy calculated at different temperatures and pressures indicates that hydrogen molecules can be reversibly stored over the Li8SiG system, and it is noted that adsorbed H2 begins to desorb at 280 K, with complete desorption at 400 K and 20 atm (or lower). AIMD simulations are further performed to authenticate the H2 desorption at various temperatures, which agrees well with the occupation number analysis. All the outcomes advocate for efficient reversible hydrogen storage over the proposed host material.

Extraction of High Time-frequency Energy Concentration of Sensor’s EMI Signals Based on Generalized Correntropy Criterion and VMD

Extraction of High Time-frequency Energy Concentration of Sensor’s EMI Signals Based on Generalized Correntropy Criterion and VMD

Investigating the decomposition mechanism of CL-20/MTNI cocrystal explosive under high temperature and high pressure using ReaxFF/lg molecular dynamics simulations

The CL-20/MTNI cocrystal, as a novel energetic material (EMs), possesses the advantages of high energy content and low sensitivity, making it a promising substitute for traditional EMs. However, the thermal decomposition mechanism of this cocrystal has not been thoroughly investigated. Therefore, we utilized the ReaxFF/lg force field to study the thermal decomposition of CL-20/MTNI cocrystal at different temperatures (2500, 2750, 3000, 3250, and 3500 K) and pressures (3000 K/0.5 GPa, 3000 K/1.0 GPa, and 3000 K/1.5 GPa). The evolution of species, initial decomposition mechanisms, and changes in the number of final products were analyzed. The results indicate that hexanitrohexaazoisowuzane (CL-20) completely decomposes within 55 ps, while 1-methyl-2,4,5-trinitroimidazole (MTNI) decomposes completely within 110 ps, suggesting that CL-20 has lower thermal stability compared to MTNI. The high-temperature decomposition of CL-20/MTNI cocrystal exhibits three main possible reaction pathways. Firstly, the denitration of CL-20 occurs, followed by the denitration of MTNI, and finally, the nitro group isomerization of MTNI. This indicates that the nitro groups in CL-20 have lower thermal stability compared to those in MTNI within the CL-20/MTNI cocrystal. Analysis of the five final products reveals that the quantities of NO2 and NO are higher than other species, attributed to the higher nitrogen and oxygen content in the CL-20/MTNI cocrystal structure. As the temperature increases, the decomposition and conversion of NO2 are accelerated, leading to a sharp decrease in the quantity of NO2 and an increase in the content of NO. However, when the pressure increases, both the quantities of NO2 and NO exhibit a trend of initially increasing and then decreasing, with a noticeable increase in the quantity of N2. This indicates that high pressure accelerates the thermal decomposition of NO2 and NO.

Enhanced Micro-Doppler Feature Extraction Using Adaptive Short-Time Kernel-Based Sparse Time-Frequency Distribution

The extraction of the micro-Doppler (m-D) feature based on time-frequency distribution (TFD) is of great significance for target detection and identification. To improve the feature extraction performance, numerous TFDs have been developed, with the majority falling under Cohen’s class. Nevertheless, these TFDs basically face a trade-off between artifact suppression and energy concentration. The main reason is that each Cohen’s class TFD is constructed by applying the two-dimensional Fourier transform to a kerneled ambiguity function directly, while existing kernels generally attenuate artifacts at the expense of losing valuable information. In this paper, a TFD reconstruction method employing an adaptive short-time kernel (ASTK) is developed in the framework of sparse representation (SR) theory to overcome this trade-off and enhance the m-D feature. Firstly, the task of the optimal kernel is explained from the viewpoint of the instantaneous auto-correlation function (IAF). Secondly, based on the quasi-linear frequency modulation feature of most m-D signals during short-time periods, the distribution rule of the short-time IAF (STIAF) in the ambiguity plane is concluded. Guided by this rule, an ASTK that can effectively remove unwanted artifacts with the least information loss is designed. Finally, an SR-based reconstruction procedure is conducted on the kerneled STIAF to generate an artifact-free TFD with high energy concentration, which can effectively enhance the m-D feature. Experiments using both simulated and real-world m-D signals demonstrate the effectiveness of the proposed method.

Enhancing Biodiesel-Methanol blends with 1-Butanol for stable and efficient fuels

The quest for sustainable fuels has led to the exploration of biodiesel as an eco-friendly alternative to conventional fossil fuels. While biodiesel holds promise due to its renewable nature and lower emissions, challenges occur when blending it with methanol. This study addresses these issues by adding 1-butanol as a cosolvent in biodiesel-methanol blends, improving their stability and performance. Gas chromatography mass spectrometry identifies the dominant compound in biodiesel as 2,6-di-tert-butylphenol, known for its stability-enhancing properties. Adding alcohols to biodiesel aiming to reduce the ignition delay time in and shorten the combustion time in diesel engines. The scientific explanation regarding the role of 1-butanol in stabilizing the biodiesel-methanol blend has not yet been revealed. Methanol's tendency to form an unstable mixture due to water affinity is mitigated by 1-butanol, which raises the critical phase separation temperature, a key indicator of blend stability. The study validates that adding 1-butanol produces a stable, homogenous blend. 1-butanol's as a third fuel blend option is underscored by its higher energy content, lower volatility, and reduced hydrophilicity compared to ethanol and methanol, making it a valuable advantage for fuel development. Investigations into ignition delay and burning speed reveal their difference with blend compositions. In conclusion, 1-butanol appears as a promising solution for enhancing the efficiency and stability of biodiesel-methanol blends, contributing to the development of sustainable and eco-friendly fuels for a more responsible and energy-efficient future.