In the last decade, a higher level of reliability has become a compulsory demand when it comes to modern DC-DC converters. This work addresses the main reliability metrics: in many studies, the failure rate λ and MTBF of an output capacitor bank used within a high-current low-voltage buck converter have shown that the output capacitor bank is the most critical component within the converter. Many authors dealt with this issue by performing reliability predictions. The majority of studies use only one specific standard prediction to solve the problem. Herein, the calculation was performed using both the older standard, MIL-HDBK-217, and the latest one, Telcordia SR-332, providing a benchmark comparison between the two, which is a helpful tool for output capacitor selection in early-stage design. The military standard was well accepted for decades in reliability prediction, even in industrial electronics, and is still used today in a critical manner because there have been no more updates after the latest version, MIL-HDBK-217F—Notice 2, was released in 1995. Since then, newer prediction standards have appeared in the electronics reliability market. Over time, this standard was mostly used, but it does not accurately model the reliability because of a lack of taking account of the mission profile. The above-mentioned newer standard—i.e., Telcordia SR-332—also tries to compensate for the lack of the newest component technology in the older standard (which is the first standard released on the market), supplying useful design data for design engineers who use the so-called “design with reliability in mind” concept. This provides the designer of DC-DC converters with a comparison between the reliability values when the two mentioned standards are used. This paper establishes the environmental condition for the passive components by means of a point of load (PoL) buck converter that is used for both calculation methods. The influence of temperature and several specific concepts, like reference conditions, operating conditions, ripple, and internal self-heating, were taken into account in order to display the results. The temperature for the capacitor’s capsule needed in πT stress factor calculation was derived using PSPICE simulation. High-fidelity and dedicated SPICE models provided by the manufacturer were used for MOSFETs, polymer electrolytic, and MLCC capacitors that comprise the converter.
Solar Chimney Power Plants (SCPP) consist of three main components: solar collector, chimney and turbine. Air under the collector is heated by the greenhouse effect, the air density is reduced and the air flows toward the chimney located at the center of the collector. Thus, electricity is produced at the turbine mounted at the entrance of the chimney. In this study, measurements have been carried out on the Solar Chimney Power Plant (SCPP) system built at Ad & imath;yaman University Campus area, with specifications 15 m in height, 0.8 m in diameter of chimney, 0.004 m thick transparent glass floor and a collector having maximum of 27 m in diameter. For this purpose, air flow rate and temperature in the chimney at certain times of the day, ambient temperature, ambient wind speed, ground temperature heated by the greenhouse effect of the collector, temperature and air velocity under the collector, the number of revolutions of turbines of different diameters and Ad & imath;yaman solar radiation values were evaluated. In this study, it has been determined that solar radiation, ambient temperature, chimney height and diameter, solar radiation absorption rate of the ground under the collector are the parameters that affect the efficiency performance of the system. It is also observed that temperature and air velocity at the point where the turbine assembly is located are maximum. In addition, it was determined that the turbine model with a diameter of 0.8 m was the most efficient model for the system. It is concluded that Solar Chimney Power Plant (SCPP) can be considered as alternative energy sources for Ad & imath;yaman.
The usage of clean energy sources, like solar energy, has been becoming more and more important because of the scarcity of fuel reserves and the need to reduce emissions of carbon to prevent global warming. In this context, a nanofluid-based PV/T (photovoltaic thermal) system has been developed to boost solar energy utilization for a variety of residential and industrial applications. The PV/T system pumps the SiO2 -nanofluid through the lowest part of the panel, decreasing the temperature of solar panel and increasing the overall amount of electricity produced. Furthermore, the heat generated through the panel can be used to raise the SiO2 nanofluid's temperature. This temperature may be utilized later to heat the building's interior or provide hot water. To evaluate the performance of the PV/T system and the existing PV system under identical weather conditions, comparative measurements were made. The results showed that the PV/T system improves the PV system in terms of power generation efficiency because it utilizes the nanofluid (SiO2) as the working fluid. Additionally, the working (SiO2) nanofluid can be utilized for heating and supply of hot water because the PV/T system raised its temperature at the outlet to about 2-2.5%. SiO2 nanofluid-based PV/T systems may, on average, significantly increase solar power utilization, more than two times that of traditional PV systems. The PV/T system is simple to install in buildings and needs minimal maintenance or repair. As a result, this technology may help to lower carbon emissions and encourage the use of renewable energy in various applications.
This paper presents an experimental study of the effect of the mass of dust retained on a fibrous filter bed operating singly and in a “cyclone-filter-bed” system on changes in filtration efficiency and accuracy, as well as the increase in flow resistance. The research was carried out using a novel and unprecedented method, determining the dust absorption coefficient km of the filter baffle under laboratory conditions. A filtration system built of a single cyclone and a cylindrical filter cartridge with an appropriately sized surface set behind it was studied. Conditions corresponding to the actual operating conditions of the air filter were maintained: dust concentration, filtration speed and dust extraction from the cyclone settling tank. The purpose of the research was to evaluate filter materials with different structures in terms of filtration efficiency and accuracy, as well as flow resistance. The study showed that the parameters of the structure of filter materials—permeability, grammage and thickness—affect the process of retaining dust particles. It was shown that the increase in the flow resistance of the filter bed has a higher intensity when dust grains of small sizes are directed at it, which is the case when the bed is operated behind a cyclone, which separates larger dust grains from the air. There is a reduction in the operating time of the filtration system due to the limitation of the permissible resistance ∆pfdop, and the corresponding dust absorption km has a lower value. For a fixed value of the flow resistance, the dust absorption coefficient km2 of three different filtration baffles AC, B2, and B, working with a cyclone, take values 50–100% smaller than when working in a single-stage system. It has been shown that the “cyclone-filter baffle” unit, due to its greater dust separation capability, allows the filter cartridge to operate for a longer time until a certain flow resistance is reached. This allows the unit to operate longer at lower flow resistance without changing the filter cartridge, thus saving energy. The km values obtained during the tests, using the proposed original method, allow the selection of the filter bed for specific vehicle operating conditions by modelling its course.
The rise of an integrated energy system requires the integration of multiple sources of energy to be embraced and transited over the power grid; that means the information and communication systems of traditional power systems will be extended, and their complexity will be increased. As the information and communication systems play a more important role in the infrastructure of the power system, a cyber-attack on them may have an impact on the power system and cause a serious threat to the integrated energy system. To analyze the threat to the complex and integrated system, some researchers provide some modeling methods to study the impact of cyber-attacks on the information and communication systems, such as the Attack Tree Model, Attack Graph Model, Petri Net Model for cyber-attack, Attack Description Language Model, State Transition Graph Model, etc. However, these modeling methods have some shortcomings. For example, they cannot describe the systematical cyber-attack and show the secure status during the cyber-attack; it is hard for them to analyze the larger and more complicated information and communication systems. To overcome the shortages, in this paper, a correlated matrix-based object-oriented model is proposed for cyber-attack modeling. With this model, the relationship between the attacker and victim can be directly built; the cyber-attack path and packets from the attacker can be tracked; and the status of the nodes and links can be shown during a cyber-attack. There are two steps to build the cyber-attack model. Firstly, the procedure and approach of the cyber-attack will be modeled by an object-oriented method; then, a correlated matrix model will be built for network topology, attack path, and attack procedure. By combining these two models, the whole cyber-attack model is created. Finally, to demonstrate the modeling method and its benefits, we use the MITM (Man-in-the-middle Attack) attack on measurement data of an AVC (Automation Voltage Control) system as examples, and build a hardware-in-the-loop (HIL) co-simulation platform to verify the model.
A general rise in environmental and anthropogenically induced greenhouse gas emissions has resulted from worldwide population growth and a growing appetite for clean energy, industrial outputs, and consumer utilization. Furthermore, well-established, advanced, and emerging countries are seeking fossil fuel and petroleum resources to support their aviation, electric utilities, industrial sectors, and consumer processing essentials. There is an increasing tendency to overcome these challenging concerns and achieve the Paris Agreement’s priorities as emerging technological advances in clean energy technologies progress. Hydrogen is expected to be implemented in various production applications as a fundamental fuel in future energy carrier materials development and manufacturing processes. This paper summarizes recent developments and hydrogen technologies in fuel refining, hydrocarbon processing, materials manufacturing, pharmaceuticals, aircraft construction, electronics, and other hydrogen applications. It also highlights the existing industrialization scenario and describes prospective innovations, including theoretical scientific advancements, green raw materials production, potential exploration, and renewable resource integration. Moreover, this article further discusses some socioeconomic implications of hydrogen as a green resource.
The temporal resolution of the demand and generation profiles may have a significant impact on the estimation of self-sufficiency and self-consumption for consumers and prosumers. As an example, measuring the load profile, with a low temporal resolution, may lead to the under-estimation of energy consumption, while measuring solar irradiation with a low temporal resolution may lead to the over-estimation of on-site energy generation. Storage systems may reduce errors due to the lower temporal resolution by 8–10 times or even more, depending on the capacity of the batteries. Besides self-generation and self-consumption, there are other indicators that can be influenced by temporal resolution that deserve to be investigated. This is a detailed study of the influence of temporal resolution and the time averaging on a hybrid photovoltaic-battery system; this study encompasses both economic and technical aspects, from the calculation of savings on the electricity bill to the estimation of the equivalent cycles of battery storage system. To this end, the three-minute load profile of a real case study is used to obtain other three load profiles with temporal resolution equal to 15, 30, and 60 min via data averaging. Therefore, the authors analyze the influence and the impact of temporal resolution and data averaging in terms of: The size of the photovoltaic generator and the capacity of the storage system; the savings in the electricity bill and the balance between costs and savings; the peak values and the average values of power flows during high generation and low generation; the profile of the storage system over the year; the utilization rate of the storage system and the rated power of the electronic converter that regulates the charge and the discharge; the profile of the state of charge of the storage system and the life-time estimation of batteries through the calculation of the equivalent number of cycles.
Concentrated animal feeding operations (both slaughter and dairy cattle) lead to land, water, and air pollution if waste storage and handling systems are not effectively managed. At the same time, cattle biomass (CB), which includes both slaughter/feedlot biomass (FB) and dairy biomass (DB), have the potential to be a source of green energy at coal-fired power plants. Part I presented results on NOx reductions with pure FB or Coal: FB blends as reburn fuels. Part II deals with results from reburning with pure DB or Coal: DB blends as reburn fuels. A mixture of NG with a small amount of NH3 was used to generate the baseline NOx of 400–420 ppm (or 185–194 g/GJ). NOx emissions were found to be reduced by as much as 96% when reburning with FB. The effects of reburn fuel type, equivalence ratio (ERRBZ) in the reburn zone, vitiated air, several injection configurations of reburn fuel and initial NO concentrations on NOx emissions were investigated. The ERRBZ shows a significant effect on the NOx reduction. The 20% heat input by reburning was the better operating condition for the long-term operation due to its ash production. The results reveal that reburn with DB fuels is an effective technology for NOx emission control when the initial NOx emission is higher than 275 ppm (or 127 g/GJ or 0.3 lb/MMBtu).
Quantitative evaluation of the antioxidant capacity of foods is of great significance for estimating food’s nutritional value and preventing oxidative changes in food. Herein, we demonstrated an easy and selective colorimetric method for the total antioxidant capacity (TAC) assay based on 3,3’,5,5’-tetramethyl-benzidine (TMB), hydrogen peroxide (H2O2) and synthetic Lycium barbarum polysaccharide-iron (III) chelate (LBPIC) with high peroxidase (POD)-like activity. The results of steady-state kinetics study showed that the Km values of LBPIC toward H2O2 and TMB were 5.54 mM and 0.16 mM, respectively. The detection parameters were optimized, and the linear interval and limit of detection (LOD) were determined to be 2–100 μM and 1.51 μM, respectively. Additionally, a subsequent study of the determination of TAC in six commercial fruit and vegetable beverages using the established method was successfully carried out. The results implied an expanded application of polysaccharide-iron (III) chelates with enzymatic activity in food antioxidant analysis and other biosensing fields.
Electrical utilities have relied upon potential transformers (PTs) and current transformers (CTs) for very accurate metering and to provide reliable signals for protective relays. Less expensive alternative sensing technologies offer the possibility of wider deployment, particularly in grids that employ distributed energy resources. In this work, the performance of an advanced medium-voltage sensor is compared with that of a reference PT and a CT and experimentally evaluated for different power grid scenarios on an advanced outdoor power line sensor testbed at the U.S. Department of Energy's Oak Ridge National Laboratory. The sensor is based on a capacitive divider for voltage monitoring and a Rogowski coil with an integrator for current monitoring. The advanced outdoor power line sensor testbed has a real-time simulator that is used to generate transient scenarios (e.g., electrical faults, capacitor bank operation, and service restoration), while the analog signals are recorded by the same high-resolution power meter. The behaviors of analog signals, harmonic components, total harmonic distortion, and crest factors are assessed for this power line sensor and compared with those of the reference PT/CT because of the absence of testing standards for advanced outdoor power line sensors.
The EU has several directives aiming toward carbon neutrality and is attempting to promote and encourage individual electricity consumers to participate in this endeavor. The key idea behind consumer awakening and activation is to push consumers to become aware of their electricity consumption behavior. The purpose of this paper was to examine the current consumption behavior of Finnish electricity consumers and their intention to support the goals of carbon neutrality through energy efficient consumption. The aim was to reveal how far the consumption behavior of people was from the intention to tackle climate change. To reach this goal, a qualitative research method was applied to evaluate the consumer awareness and intentions. A consumer survey was conducted to enable standardized and consistent data collection. The research utilized a key performance indicator (KPI) approach to evaluate the results: the social KPIs connected with qualitative values provide a comprehensive approach. According to the results, the awareness of consumers of their consumption behavior was not very high, and some data needs can be identified. In addition, clear intentions can be detected among the residents to support the environment and to save energy. However, the consumers did not seem to be aware of the available data and existing services that could help them to improve their energy efficiency. Therefore, more motivation and communication is still required to affect the electricity consumption behavior.
Shape-from-Focus (SFF) methods have been developed for about twenty years. They able to obtain the shape of 3D objects from a series of partially focused images. The plane to which the microscope or camera is focused intersects the 3D object in a contour line. Due to wave properties of light and due to finite resolution of the output device, the image can be considered as sharp not only on this contour line, but also in a certain interval of height—the zone of sharpness. SSFs are able to identify these focused parts to compose a fully focused 2D image and to reconstruct a 3D profile of the surface to be observed.
A small perturbation on the shoreline may develop under high-angle wave conditions, resulting in the formation of sand spits along the shoreline. Serizawa et al. explained the development of sand spits caused by the instability mechanism using the BG model (a model for predicting 3-D beach changes based on Bagnold’s concept). However, examples of the development of sand spits caused by this mechanism in the field are limited in number. Lingayen Gulf in the Philippines has a large aspect ratio, so shoreline instability occurs along the coastline, significantly affecting the shore protection along the coast. In this study, the shoreline instability along the river delta coasts around the Balili and Aringay Rivers flowing into Lingayen Gulf and a sand spit were investigated using satellite images together with field observation. The shoreline changes observed south of the Aringay River mouth were compared with those observed in a previous study on the development of a sand spit by San-nami et al. The rate of longshore sand transport to form a sand spit at Santo Tomas in Lingayen Gulf was estimated to be approximately 1.3 × 105 m3/yr, which is in good agreement with the value measured on the Shimizu coast in Suruga Bay, with a comparable aspect ratio of 1.2 relative to 1.3 in Lingayen Gulf. It was concluded that shoreline undulations have evolved downcoast of two river deltas owing to high-angle wave instability along the east coast of Lingayen Gulf and the formation of a sand spit has occurred. A soft measure, such as sand bypassing, would be better to be adopted along the coasts in Lingayen Gulf instead of hard measures against erosion, to prevent rapid expansion of an artificial, protected coastline.
Concerns over the past few decades have focused, more than ever, on finding and implementing efficient, handy, and renewable sources to reduce pollution. Biomass, in general, and biomass from annual vine cuttings, are renewable sources that can be used by a large amount of the population. Biomass densification in the form of briquettes is an efficient method of obtaining a biofuel with the same characteristics as wood. The production of densified material as a briquette consists of sampling, drying naturally, chopping, grinding and briquetting the vine cuttings. The obtained results showed that the size of the briquettes met the requirements imposed by the standard, with a length between 185 mm and 400 mm and a diameter of 58 ± 0.75 mm, the humidity of the briquettes varying between 5.42%, at Sauvignon Blanc and 7.98% for Pinot Noir, while the durability of the briquettes registered minimum values of 98.17% for Muscat Ottonel and a maximum of 99.14% for Feteasca Neagra, and a unit density with values between 1227 kg/m3 for Feteasca Alba and 1389 kg/m3 for Pinot Noir. The conclusions of these experiments are promising, showing that the densification of biomass from vines cuttings qualifies within the standard requirements for obtaining a valuable biofuel.
The epidemic of cardiovascular diseases (CVDs) is predicted to spread rapidly in advanced countries accompanied by the high prevalence of risk factors. In terms of pathogenesis, the pathophysiology of CVDs is featured by multiple disorders, including vascular inflammation accompanied by simultaneously perturbed pathways, such as cell death and acute/chronic inflammatory reactions. Epigenetic alteration is involved in the regulation of genome stabilization and cellular homeostasis. The association between CVD progression and histone modifications is widely known. Among the histone modifications, histone methylation is a reversible process involved in the development and homeostasis of the cardiovascular system. Abnormal methylation can promote CVD progression. This review discusses histone methylation and the enzymes involved in the cardiovascular system and determine the effects of histone methyltransferases and demethylases on the pathogenesis of CVDs. We will further demonstrate key proteins mediated by histone methylation in blood vessels and review histone methylation-mediated cardiomyocytes and cellular functions and pathways in CVDs. Finally, we will summarize the role of inhibitors of histone methylation and demethylation in CVDs and analyze their therapeutic potential, based on previous studies.
Background Recognition of disorder phenotypes may help to estimate prognosis and to guide the clinical management. Current cough management guidelines classify patients according to the duration of the cough episode. However, this classification is not based on phenotype analyses. The present study aimed to identify cough phenotypes by clustering. Methods An email survey among employed, working-age subjects identified 975 patients with current cough. All filled in a comprehensive 80-item questionnaire including the Leicester Cough Questionnaire. Phenotypes were identified utilizing K-means partitional clustering. A subgroup filled in a follow-up questionnaire 12 months later to investigate the possible differences in the prognosis between the phenotypes. Results Two clusters were found. The cluster A included 608 patients (62.4% of the population) and the cluster B 367 patients (37.6%). The three most important variables to separate the clusters were the number of the triggers of cough (mean 2.63 (SD 2.22) vs. 6.95 (2.30), respectively,p < 0.001), the number of the cough background disorders (chronic rhinosinusitis, current asthma, gastroesophageal reflux disease, 0.29 (0.50) vs. 1.28 (0.75), respectively,p < 0.001), and the Leicester Cough Questionnaire physical domain (5.33 (0.76) vs. 4.25 (0.84), respectively,p < 0.001). There were significant interrelationships between these three variables (eachp < 0.001). Duration of the episode was not among the most important variables to separate the clusters. At 12 months, 27.0% of the patients of the cluster A and 46.1% of the patients of the cluster B suffered from cough that had continued without interruptions from the first survey (p < 0.001). Conclusions Two cough phenotypes could be identified. Cluster A represents phenotype A, which includes the majority of patients and has a tendency to heal by itself. The authors propose that cluster B represents phenotype TBQ (Triggers, Background disorders, Quality of life impairment). Given the poor prognosis of this phenotype, it urges a prompt and comprehensive clinical evaluation regardless of the duration of the cough episode.
The aim of this paper is to analyze the performance of commercial fuel cell (rated capacity 1000W) with the help of resistive load and output power variation with change in H-2 flow rate and calculate the maximum power point (MPP) of the proton exchange membrane (PEM) while changing AC and DC load respectively. The factors influencing the output power of a fuel cell are hydrogen flow rate, cell temperature, and membrane water content. The results show that when the H-2 flow rate is changed from 11, 13, and 15 Lpm, MPP is increased from lower to higher flow rate. The power of the fuel cell is increased at the rate of 29% by increasing the flow rate from 11 to 15 lpm. This study will allow small-scale industries and residential buildings (in remote or inaccessible areas) to characterize the performance of PEMFC. Furthermore, fuel cell helps in reducing emission in the environment compared to fossil fuels. Also, fuel cells are ecofriendly as well as cost effective and can be the best alternative way to convert energy.
An ex-situ gravitational fixed bed pyrolysis reactor was used over Al2O3 supported Ni2P based catalyst with various Ni/P molar ratios (0.5-2.0) and constant nickel loading of 5.37 mmol/g Al2O3 to determine the hydrodeoxygenation of rubberwood sawdust (RWS) at atmospheric pressure. The 3D catalysts formed were characterized structurally as well as acidic properties were determined by hydrogen-temperature programmed reduction (TPR). The Ni2P phase formed completely on Al2O3 for 1.5 Ni/P ratio, although lesser crystallite sizes of Ni2P were seen at Ni/P ratios less than 1.5. Additionally, it was shown that when nickel loading level increased, acidity increased and specific surface area dropped, probably because nickel phosphate is not easily converted to Ni2P. When Ni/P ratio was 1.5, Ni2P phase fully formed on Al2O3. The catalytic activity was explained in terms of impacts of reaction temperature and Ni/P molar ratio. At relatively high temperature of 450 degrees C, the high-value deoxygenated produce was predominantly composed of n-alkanes. Based on the findings, it was suggested that hydrogenolysis, hydrodeoxygenation, dehydration, decarbonylation, and hydrogenation are all part of mechanism underlying hydrotreatment of RWS. In conclusion, the synthesized Ni2P/Al2O3 catalyst was capable of deoxygenating RWS with ease at atmospheric pressure, primarily resulting in long chained (C9-C24) hydrocarbons and acetic acid.
Hypertension in childhood leads to hypertension in adult life, the strongest risk factor being obesity. This study determined the prevalence of primary hypertension and its risk factors in Grade XII learners in KwaZulu-Natal, South Africa, from March 2016 to June 2017. Weight, height, body mass index (BMI), random finger prick cholesterol and glucose, and spot urine for an albumin : creatinine ratio were measured. An average of three separate blood pressure readings taken was at least 5 minutes apart. Five hundred and sixty-four learners had weight, height, and BMI; 536 had random blood glucose; and 545 had cholesterol and random spot urine albumin : creatinine ratios measured. Prehypertension was detected in 168 (29.7%) and hypertension in 77 (13.7%) of learners. Ninety (15.9%) were overweight and 75 (13,3%) were obese. Hypercholesterolaemia was present in 58 (10.8%) and a high spot random urine albumin : creatinine ratio in 5 (1.0%). None had a high blood glucose level. Both prehypertension and hypertension in all learners showed a significant increase with increasing BMI. Six (1.0%) learners had metabolic syndrome. Female learners in other racial groups (defined as Indian, mixed race, and White learners), overweight, and obese learners showed significantly higher rates of hypercholesterolaemia. We showed overweight and obesity as risk factors for prehypertension and hypertension. This presages the need for an appropriate diet and adequate exercise in a child's school career.
Biodiesel is a non-polluting and non-toxic energy source that can replace conventional diesel. However, the higher production cost and raw material scarcity became challenges that obstruct the commercialization of biodiesel production. In the current investigation, fried cooking oil is used for biodiesel production in a hydrodynamic cavitation reactor, thus enhancing raw material availability and helping better waste oil disposal. However, due to the cavitation effect inside the reactor, the hydrodynamic cavitation reactor can give biodiesel yield above 98%. Thus, the use of orifice plates (having a different number of holes for cavitation) in the reactor shows more than 90% biodiesel yield within 10 mins of a time interval. The effects of rising temperature at different molar ratios are also investigated. The five-hole plate achieves the highest yield for a 4.5:1 molar ratio at 65 degrees C. And the similar result is predicted by the response surface methodology model; however, the optimized yield is obtained at 60 degrees C. The investigation will help understand the effect of hydrodynamic cavitation on biodiesel yield at different molar ratios and elevated temperatures.
