Breakdown Of Structure Research Articles

Cavitation erosion risk on a hydrofoil using a multi-scale method

The present study employs a two-way coupled multi-scale method to simulate and analyze the cloud cavitation flow around a hydrofoil, based on which the distribution of cavitation erosion risk on the hydrofoil is evaluated. The numerical results demonstrate that the multi-scale method can capture not only the overall evolution characteristics of cloud cavitation but also the generation, growth, and collapse of small-scale bubbles. Throughout the majority of a cavitation cycle, the scale of the Lagrange bubbles roughly follows a logarithmic Gaussian distribution. However, it shows a double-peak characteristic as a result of bubble production from both the sheet cavity and the shedding cloud. The distribution of local erosion risk, which is closely aligned with experimental findings, is assessed based on the collapse of small-scale bubbles. The erosion risk is greatest near the closure line of the sheet cavity, which is due not only to the collapse of bubbles around the shedding cloud but also to the shedding and breakdown of small-scale vapor structures during the development of the reentrant jet. During the cavitation cycle, the erosion risk is highest when the shedding cloud forms and the erosion risk decreases as it moves downstream. The multi-scale numerical analysis reveals that the cavitation number alone is insufficient for characterizing cavitation and its erosive effects. For a given cavitation number, the mean diameter of Lagrange bubbles increases with the inflow velocity. Furthermore, the total impact energy from bubble collapse on a hydrofoil follows a power-law dependence on the inflow velocity.

Encapsulation of Fatty Acids Using Linear Dextrin from Waxy Potato Starch: Effect of Debranching Time and Degree of Unsaturation

This study investigates the effects of the debranching time of waxy potato starch using pullulanase and recrystallization on particle morphology, debranching degree, and crystal structure. The results demonstrated that after gelatinization and debranching, the surface of the starch crystals became rough and uneven due to hydrolysis, with most particles showing a fragmented surface. The crystalline state was not significantly changed with debranching time. X-ray diffraction analysis revealed no significant differences in the patterns of recrystallized linear dextrin (LD) after various debranching times. Notably, the short-range ordered structure of LD after debranching and recrystallization was more organized than that of the original or gelatinized starch. Additionally, polarized light microscopy showed that the birefringent pattern disappeared as a result of debranching and recrystallization, indicating the breakdown of particle structure, although the overall particle morphology did not change significantly with varying debranching times. Furthermore, linear dextrin derived from starch debranched for 6 h (with pullulanase at 15 μg/g) successfully embedded stearic acid, oleic acid, and linoleic acid, forming a VI-type starch–fatty acid complex.

First-principles study of structural, elastic, electronic, transport properties, and dielectric breakdown of Cs2Te photocathode

The pursuit to operate photocathodes at high accelerating gradients to increase brightness of electron beams is gaining interests within the accelerator community, particularly for applications such as free electron lasers (FEL) and compact accelerators. Cesium telluride (Cs2Te) is a widely used photocathode material and it is presumed to offer resilience to higher gradients because of its wider band gap compared to other semiconductors. Despite its advantages, crucial material properties of Cs2Te remain largely unknown both in theory and experiments. In this study, we employ first-principles calculations to provide detailed structural, elastic, electronic and transport properties of Cs2Te. It is found that Cs2Te has an intrinsic mobility of 20 cm2/Vs for electrons and 2.0 cm2/Vs for holes at room temperature. The low mobility is primarily limited by the strong polar optical phonon scattering. Cs2Te also exhibits ultralow lattice thermal conductivity of 0.2 W/(m*K) at room temperature. Based on the energy gain/loss balance under external field and electron–phonon scattering, we predict that Cs2Te has a dielectric breakdown field in the range from ~ 60 to ~ 132 MV/m at room temperature dependent on the doping level of Cs2Te. Our results are crucial to advance the understanding of applicability of Cs2Te photocathodes for high-gradient operation.

The Linguistics of Humour in Harold Pinter

This paper is an extract from a PhD dissertation on the language of humour in literary texts. The study belongs to the domain of linguistics of literary humour, a domain that has long been unrecognized due to focus on jokes as the form of humour (e.g. Raskin 1985, Zhao 1988, Zadjman 1993, Norrick 2003, Veale et al 2006 …etc.). The study deals with the linguistic analysis of humour in selected extracts from The Birthday Party (1958), and No Man's Land (1974) by the British Nobel Prize dramatist, Harold Pinter (1930 – 2008). Incongruity has been consistently cited in the literature as the major cause of humour. It describes the cognitive basis of humour, which has its origin in the cognition of both speaker and hearer. The present research used a Complementary Pragmatic approach, with a kit of five Pragma-linguistic tools, to detect humorous incongruity in the extracts analysed. Generally, the results prove that linguistic humour in the data analysed tends to be pragmatic in that Pinter uses ordinary language extraordinarily. There is no play on words, nor breakdown of linguistic structures. Humour in the extracts analysed comes from the mismatch between the linguistic communicative strategy and the discourse context rather than from breakdown of linguistic structures.

DEMOGRAPHY OF AGEING POPULATION IN NIGERIA: TRENDS, CHALLENGES AND IMPLICATIONS

Nigeria, like many other African countries, is experiencing a rapidly ageing population, with significant implications for healthcare, social security, and economic growth. Lack of functional national policy on the care and welfare of older persons in Nigeria, the breakdown of the family structure and the absence of a social security system, present unique challenges to the elderly in Nigeria. This paper analyzes the demography of the ageing population in Nigeria with a focus on the trends, challenges, and implications for healthcare, social security and economic growth. The paper relied on secondary sources of data such as journal articles and books in the area of the ageing population in Nigeria for its analysis. The Disengagement Theory provided theoretical pathway for the study. Based on the review, it was found that the rapidly ageing population poses challenges to Nigeria’s development including strains on social security system, increased healthcare costs, and potential decline in economic productivity. These challenges are due to lack of policies and the appointment of personnel capable of understanding and responding to the current social priorities and complex needs of an increasingly aging population in the country. The paper recommends among others, the need for policy makers to put in place, functional policies towards a robust public pension, insurance and healthcare system to ensure a more sustainable and equitable future for the ageing population in Nigeria.

İlahiyat Fakültesi Erkek Akademisyenlerinin Kadına Yönelik Şiddet Algısı ve Çözüm Önerileri

In recent years, a significant increase in violence against women has emerged as a severe issue negatively impacting both women and society. This violence encompasses various forms, including physical, sexual, economic, psychological, and, increasingly, cyberbullying due to the widespread use of the internet. Research on violence against women and news reports commonly identify men as the perpetrators of such acts. The desire for control and interpretations based on religion can justify these acts of violence. Consequently, this study aims to discern the perspectives of male scholars in theology faculties regarding violence against women (VAW), its underlying causes, and potential solutions. To achieve this objective, a qualitative research method known as the multiple case study design was employed. The study group consisted of 25 male scholars selected through convenient sampling. Data were collected through interviews with the participants and subsequently analyzed using thematic content analysis. To effectively resolve and eliminate a problem, it is essential first to identify and accurately understand its root causes. In this context, the definitions of VAW provided by male scholars reflect subjective processes and perceptions. Their statements regarding the causes of VAW and recommendations for solutions generally revolve around the disruption of family order and values, leading to the breakdown of societal structures, particularly regarding their physical and psychological dimensions. Participants who emphasize the necessity of societal change to prevent VAW have highlighted the importance of incorporating practices into daily life that promote social awareness, equality, and justice. From this perspective, it can be argued that there is a pressing need to integrate educational policies and practices into daily life that can critically examine cultural and societal norms, transform perceptions and practices that trigger violence, and actively contribute to solving this problem. * This article is the revised and developed version of conference presentation entitled “Perceptions and Solutions of male Academicians in the theologhy Faculty Regarding Violence Against Women”, orally delivered at the 4th Turkish Symposium of Social Sciences.

High performance COVID-19 screening using machine learning.

Since the World Health Organization declared the Coronavirus Disease 2019 (COVID-19) pandemic as an international concern of public health emergency in the early 2020, several strategies have been initiated in many countries to prevent healthcare services breakdown and collapse of healthcare structures. The most important strategy was the increased testing, diagnosis, isolation, contact tracing to identify, quarantine and test close contacts. In this context, finding a rapid, reliable and affordable tool for COVID-19 screening was the main challenge to address the pandemic. Molecular diagnosis by reverse transcriptase polymerase chain reaction (RT-PCR), even though considered as the gold standard in the diagnosis of COVID-19, was time consuming and therefore does not fit the objective of rapid screening. In addition, serological tests to detect anti-severe acute respiratory syndrome coronavirus 2 (SARS-COV-2) antibodies suffered from low sensitivity. Prediction models based on machine-learning (ML) that combined several clinical features to estimate the risk of COVID-19 have been developed. To address these screening challenges, we created a ML model (MLM) based on gradient boosting method. We included several clinical features and the daily geographic prevalence of COVID-19 cases in the MLM. The MLM was trained on 1554 cases (757 COVID-19), and tested on 547 cases (169 COVID-19). Our MLM successfully predicted RT-PCR positivity with an accuracy of 97.06%. Moreover, the variable sensitivity and specificity of our MLM depending on the disease geographic prevalence has introduced the concept of "dynamic" disease screening. In the context of future world pandemic emergencies, we believe that this MLM method can be very useful as a rapid, reliable and dynamic screening tool for contagious diseases, especially in the developing countries.

Isotopic and molecular analyses of n-alkanes in a temporal study of coastal sediment contributions to organic carbon degradation induced by algal bloom and terrestrial runoff.

The priming effect (PE) refers to the enhanced remineralization of recalcitrant organic carbon (OC) driven by the respiration of labile OC, potentially increasing CO2 fluxes from aquatic ecosystems. Patterns of PE induced by marine and terrestrial OC inputs can be explored through sedimentary contributions to the degraded OC pool. In this study, coastal sediments (δ13Cbulk=-25.26±0.06‰, 1.63±0.07% OC) were spiked with isotopically distinct marine and terrestrial OC sources (Nannochloropis phytoplankton, δ13C=-43.18±0.31‰; and C4 corn leaves, δ13C=-13.90±0.09‰). Source contributions to respired OC were investigated using n-alkane concentration profiles and stable carbon isotopes (C15-C30) across 30 microcosms. Elevated concentrations of 13C-enriched high molecular weight n-alkanes (e.g., δ13CC29=-26.3±0.5‰) were observed in corn leaf amendments, whereas the phytoplankton spike exhibited a higher abundance of 13C-depleted low molecular weight n-alkanes (e.g., δ13CC17=-46.8±0.4‰). Mixing models indicate the sedimentary OC contribution to the degraded biomarkers, for which an increasing trend suggests a PE. Phytoplankton-amended microcosms showed a sediment OC contribution of 10.3±1.5% to the degradation of the C17 n-alkane. The corn leaf spike resulted in consistently higher contributions of 30.4±3.6% for the lost C29 n-alkane, documenting the effect of carbohydrate rich organic matter on sedimentary OC remineralization. A synergistic interaction emerged when sediments received a mix of marine and terrestrial OC, exhibiting contributions to n-alkane loss of 48.3±5.3% for C17, and 35.2±5.2% for C29. Following biochemical fractionation that leads to the selective breakdown of certain biochemical structures, our data indicate greater sedimentary degradation during induced terrestrial runoff compared to an algal bloom, providing a quantitative measure of OC remineralization.

POVERTY, DECLINE OF MORALITY AND SOCIAL JUSTICE IN NIGERIA

This paper examines poverty and decline of morality and social justice in Nigeria. It is a decrease in ethical behavior and the commitment to fair treatment for all members of a community, often manifested through increased social inequality, corruption, disregard for human rights, and a growing acceptance of immoral actions, leading to a sense of societal decay and a weakening of collective values. Secondary sources of data and qualitative analysis was used for the study. Economic pressures, weak governance and corruption, cultural erosion, social fragmentation and breakdown of family structures are some drivers of decline of morality and social justice. This has led to survivalist mentality. This qualitative study explores the interconnections between poverty, morality, and social justice in Nigeria, emphasizing the transformative role of education in addressing these issues. Conflict theory was used as the theoretical framework for the study. It was recommended that Strengthen social institutions, create employment opportunities and social welfare schemes that will alleviate poverty, encourage good leadership and governance. Others are government should adopt dialogue and civil society engagement with a view to promote social justice and morality and integrate moral education into school curricula to promote values such as honesty, integrity, and respect for human rights and promote civic education to raise awareness about citizens' rights and responsibilities.

Entrainment, detrainment and dilution of dry and moist atmospheric thermals

Abstract This study examines entrainment, detrainment, and dilution of dry and moist (cloud) atmospheric thermals in large-eddy simulations. In a neutrally stable environment (with respect to dry dynamics), moist thermals have an increase in radius R with thermal height zt (α ≡ dR/dzt) about 4 times smaller compared to dry thermals when density stratification is considered, and ∼2.4 times smaller without density stratification (i.e., applying the Boussinesq approximation). An analytic expression relating α to several dimensionless parameters is derived from the thermal impulse-circulation relation to clarify the factors impacting α. This expression shows that the difference in buoyancy structure between moist and dry thermals, with buoyancy concentrated in the central cores of moist thermals owing to latent heating, explains their smaller spreading rates. Individual contributions of entrainment and detrainment are analyzed using a direct parcel-based approach in the simulations. Moist thermals have similar fractional detrainment but much smaller fractional entrainment rates compared to dry thermals, consistent with the differences in α. Despite having smaller α, moist thermals are similarly dilute (quantified by a passive tracer) as dry thermals because of their greater mixing efficiency with the environment. Thus, moist thermals are substantially dilute but expand much less in size/volume as they rise compared to dry thermals. α values for moist thermals in (dry) neutral and statically stable environments are similar, but fractional entrainment and especially detrainment rates are greater in the stable environment. Large detrainment rates are associated with a breakdown of the broader thermal vortex ring structure, especially with low environmental relative humidity, attributed in part to evaporation and buoyancy reversal.

Rural-to-Urban Migration in China and Late-Life Cognitive Trajectories: A Perspective From the Hukou System.

Migrating to urban areas profoundly shapes later-life cognitive function. However, it is unclear whether the acquisition of urban citizenship matters in old age and how the rural-urban hukou differences in cognition change over time. In particular, the existing literature has overlooked the need to differentiate between the effects of health selection and urban hukou attainment. To address these gaps, we use data from five waves of the China Health and Retirement Longitudinal Study. The results indicate that those who have obtained urban hukou through policies have better cognitive outcomes later in life compared to hukou non-converters, and these hukou-related differences grow with age. However, their cognitive abilities are lower when compared to merit-based hukou converters, who exhibit similar trajectories to lifelong urban citizens. These findings encourage not only a further breakdown of the urban-rural segregation structure in China, but more importantly, an improvement in the cognitive reserve of individuals.

Quantitative assessment of hardened leather artifact deterioration using infrared spectroscopy

This article describes a quantitative assessment method proposed to quickly identify the degree of deterioration of hardened leather artefacts. We used three techniques to artificially age samples, namely, dry-heat ageing (DH), UV-ageing (UV), and alkali-thermal ageing (AT). The deterioration mechanisms were studied via thermogravimetry/derivative thermogravimetry (TG/DTG) and attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR). Combined with amide III band deconvolution and second derivative fitting, we constructed a method for assessing the degree of deterioration by the relative content of random coils (referred to as R) in the secondary structure of the protein. The results show that with increasing ageing time, the macrostructures and microstructures of the leather changed to varying degrees. This study elucidates the differential behaviour of vegetable-tanned leather collagen under oxidative and hydrolytic mechanisms. Based on the deterioration characteristics and fitting results, we divided the hardened leather into the following three levels. Mild deterioration: 0 ≤ R ≤ 5%; leather with reduced pores and slight dryness and hardness but with a stable collagen structure; if the β-sheet content is ≥ 68% at this point, the leather may be recrosslinked by ultraviolet irradiation. Moderate deterioration: 6 ≤ R ≤ 25%; partial hydrogen bond breaking in leather, loosening of the collagen–tan matrix, dry and hard curling of the leather surface, and fibre cementation. Severe deterioration: R ≥ 40%, β-sheet ≤ 24%, and the α-helix is higher; surface reflection, severe macroscopic deformation and embrittlement, and the breakdown and gelatinization of the three-stranded helical structure of leather proteins. The quantitative analysis method was suitable for studying the deterioration mechanisms and assessing the degree of deterioration in Heishanling leather artefacts, which also provides a new practical scheme for assessing the degree of hardened leather.Graphical

Combining Thermogravimetry-Mass Spectrometry and Target Factor Analysis for Rapid Characterization of Volatiles from Degradation of Epoxy Paint.

Thermogravimetry coupled with simultaneous evolved gas analysis by mass spectrometry was used for discerning organic compounds released during the thermal degradation of paint whose chemical compositions are not readily accessible. Thermogravimetric analyses up to 600°C revealed distinct degradation patterns under inert and oxidative conditions. Significant degradation of paint initiates at around 360°C and concludes at 500°C in a nitrogen atmosphere. However, under oxidative conditions, degradation began at 100°C, with notable mass loss extending from 300 to 600°C, with a distinct event at 500°C. Moreover, the overall mass loss in air has been observed to be 3% higher than that in nitrogen. The rapid characterization of the volatiles was made possible by model-free target factor analyses of evolved gas mass spectra. The temperature-correlated mass analyses revealed potential volatile sources, including structural breakdown and oxidative conversion. Comparative analyses revealed predominantly oxidative conversion of organics to CO2 during degradation in air. The evolution of several classes of organics during the thermal degradation of paint is a matter of great concern for postulated accident scenarios in nuclear power plants. The low molecular weight organic volatiles may be taken up by iodine aerosols released into the containment during an accident, potentially forming organic iodides, which are biological hazards. Thus, identifying these volatile organics is crucial for accurately estimating the source term of volatile organic iodine.

Rheological characterization and modeling of ultra-high-velocity fluidized submarine landslides

Submarine landslides are critical phenomena due to their potential to reshape seabed topography, trigger tsunamis, and compromise offshore infrastructure. Understanding the rheological properties, particularly shear stress and viscosity under high shear rates, is essential for comprehending the dynamics of these landslides, a topic often underexplored in previous research. This study explores the rheological behavior of fluidized submarine landslides, with a focus on in-site sediments from the South China Sea and the Western Pacific Ocean. Samples prepared with varying densities were subjected to extensive rheological testing in the laboratory and analyzed under shear rates of up to 2000 s−1. Results indicated that all samples exhibited non-Newtonian fluid characteristics, showing shear-thinning behavior at low shear rates and shear-thickening behavior at higher shear rates. This transition is attributed to the breakdown of internal sediment structures, leading to changes in viscosity. This study also found that higher water content generally results in lower yield stress and consistency coefficients, while increasing the shear rate reduces the nonlinearity of the fluid's behavior. To model this complex behavior, a piecewise rheological model based on the Herschel-Bulkley framework was proposed. This model effectively captures the variations in rheological properties across different shear rate stages, with critical shear rates influenced by the sediment type and water content. These findings contribute to a deeper understanding of submarine landslides under extreme conditions, and the proposed model offers a more accurate tool for predicting the behavior of fluidized submarine landslides.

Quantitative and acoustic characteristics of ternary mixes including EDTAs: A thermodynamic study

The ternary system of water, Ethylenediaminetetraacetic acids (Disodium EDTA, Trisodium EDTA and Tetrasodium EDTA) and polyethylene glycol 4000 has had its ultrasonic velocities (s) and densities (ρ) recorded at 288.15–318.15 K at atmospheric pressure of 0.01 MPa, depending on the composition. These numbers have been used to compute the experimental volumetric and ultrasonic characteristics. Using density and speed of sound measurements, the apparent and partial molar properties along with transfer properties are investigated. The evaluation additionally includes the expansibilities (Eϕ0) and its first order derivative ∂Eϕ0∂TP. In addition, the pair and triplet coefficients are derived using liquid theory of McMillan and Mayer. These computed parameters provide light on the results in relation to the physicochemical co-solute–solvent relationship that arises in the current system under investigation. The mixes of these solutions include structures of glycol and EDTAs that are firmly bound. We analyse the findings in the context of complex structure creation and breakdown in ternary combinations. The co-sphere overlap model states that the produced parameters, which are considered the kind of interactions occurring inside the combination, are used to characterise the outcomes. Excess parameters and FT-IR spectroscopic characteristics show a good agreement, supporting the use of FT-IR to analyse particular interactions, such as the creation of hydrogen bonds among ternary liquid mixtures.

Localized enzymolysis and dual-frequency ultrasound modification of underutilized fava bean protein: Techno-functional, structural, in vitro digestibility, molecular docking, and interrelationship characteristics

This study examined the effect of using dual-frequency ultrasonic treatment (DFUT) and targeted enzymolysis on the physiochemical, structural, and techno-functional properties of the underutilized fava bean protein (FBP) and its hydrolysate (FBPH). FBP was enzymatically hydrolyzed (5–15% DH) to produce FBPH, employing alcalase as the catalyst. The enzymolysis process declined the color brightness, turbidity, and particle size for both non-sonicated and DFUT-treated FBP. Additionally, the enzymatic treatment resulted in an increase (P < 0.05) in the absolute values of zeta potential. Further, DFUT decreased water holding capacity for both FBP and FBPH compared to the untreated ones. DFUT, on the other hand, increased oil absorption capacity compared to non-sonicated ones. Additionally, XRD, FTIR, and intrinsic fluorescence spectral analyses demonstrated that FBPH exhibited a greater degree of flexibility and mobility in its secondary structures compared to FBP. Moreover, SEM and CLSM investigations provide convincing evidence that DFUT improves and speeds up the breakdown of proteins' structures, especially at higher DH. The molecular weight of DFUT-treated FBP showed a notable decrease in the SDS-PAGE profile, but there were no discernible differences between DFUT-treated and non-sonicated FBPH. The DFUT-treated FBP-10DH had significantly better in vitro digestibility (85.70%) compared to the non-sonicated FBP-15 (76.63%) and control FBP-0DH (68.57%). This indicates that the DFUT modification effectively improved the digestibility of the hydrolysate. Correlation and molecular docking research suggest that DFUT has different impacts on specific FBP and its FBPH characteristics. Taken together, localized enzymolysis and DFUT can alter the conformation of proteins and their intermolecular interactions with FBP and FBPH, potentially enhancing their functionality and expanding their utilization in the food industry.

Treatment of Cigarette Butts: Biodegradation of Cellulose Acetate by Rot Fungi and Bacteria.

This study demonstrated the biodegradation of two different brands of cigarette butts (CBs), which are primarily composed of cellulose acetate, by four distinct microorganisms. These included the white rot fungus Pleurotus ostreatus, the brown rot fungus Lentinus lepideus, and the bacteria Bacillus cereus and Pseudomonas putida. After 31 days of treatment, weight loss measurements revealed a mass loss of 24-34%, where B. cereus exhibited the greatest efficacy in terms of mass loss for both brands of CBs. Fourier-Transform Infrared Spectroscopy (FTIR), confocal microscopy, and scanning electron microscopy (SEM) confirmed changes in the surface of the CBs, attributable to structural wear and material breakdown, indicating effective biodegradation by the evaluated microorganisms. Furthermore, the analyses confirmed changes in the surface of the CBs, attributable to structural wear and material breakdown, indicating effective biodegradation by the evaluated microorganisms.

Screening, Gene Cloning and Expression of Cellulase-Producing Strain Bacillus subtilis Xh-16.

Cellulase is a complex enzyme system composed of multiple hydrolytic enzymes. It can degrade cellulose into glucose and improve the utilization efficiency of cellulose resources. Cellulase produced by microorganisms is the main method used in industry, offering the advantages of convenience and being environmentally friendly. A strain Xh-16 with high cellulase production was screened from the rotten rice straw. It was identified as Bacillus subtilis by morphological identification, physiological and biochemical identification, and 16S rRNA gene sequence analysis. Strain Xh-16 was used to degrade rice straw. After a 48h cellulase treatment, the complete degradation and structural breakdown of the straw were observed. We cloned the endoglucanase Cel5L gene of Bacillus subtilis Xh-16 and induced expression of the cloned gene in Escherichia coli BL21 (DE3). The results showed that the coding length of Cel5L gene was 1500bp, and the molecular weight of the encoded protein was about 55kDa. The molecular formula is C2456H3811N671O761S10 and it has 7709 atoms and 499 amino acids. Cel5L differs significantly from some the glycoside hydrolase family 5 cellulases because it has only one carbohydrate binding module family 3 at the C-terminus of its catalytic domain. The cellulase gene Cel5L in Xh-16 can encode active cellulase and can be heterologously expressed in Escherichia coli, which makes Escherichia coli have cellulase function. This study serves as a foundation for further research on cellulase diversity in Bacillus subtilis and offers insights for enhancing cellulase production.

Near wake evolution of a tidal stream turbine due to asymmetric sheared turbulent inflow with different integral length scales

Tidal stream turbines deployed at highly energetic open water sites are subjected to sheared inflow in the rotor plane. The inflow shear is expected to cause asymmetric loading on the rotor blades and affect the downstream wake. In the current study, two different turbulent inflow conditions, static-high shear and dynamic shear, were generated via an active-grid turbulence generator. A 1:20 scaled three-bladed horizontal axis tidal turbine model was tested in those conditions. The results were compared to a quasi-laminar case with no imposed turbulence or shear. The results show that the high shear reduces the average performance, with a drop of up to 16% in the optimal power coefficient. Besides, the shear profiles increase torque fluctuations and induce significant differences in wake hydrodynamics between the high-speed (upper) and low-speed (lower) regions. The large integral length scales further enhance the load fluctuations perceived by the rotor but have a negligible effect on the mean wake field quantities and the wake recovery. The lower half region featured a faster breakdown of tip vortex structure and a rapid drop of swirl number, a phenomenon conjectured to be a consequence of the strong turbulence intensities and Reynolds stresses in the lower half region. The sheared turbulent inflow also results in a very intensive energy redistribution process towards large-scale, low-frequency motions, which is important to the downstream turbines.

PROBABILITY OF ELECTRON TUNNELING THROUGH DIELECTRIC PORES IN SURFACE METAL LAYER

The paper presents a study of the influence of nanovoids formed in the metal surface layer on the field emission current (the first stage of the accelerator structure breakdown). It is shown that the field emission current through nanovoids has a resonant character. It was found that under resonant conditions, an increase in the current density from the copper surface by more than 3.5 times compared to the case of an unmodified surface is observed. The presence of a dielectric in the nanovoids expands the resonant region. When the resonance conditions are not met or the diameter of the nanovoids increases, the current density decreases to zero, which can be a way to prevent an accelerator structure breakdown.