Intermittent Occurrence Research Articles

Hydrophilic catheters for intermittent catheterization and occurrence of urinary tract infections. A retrospective comparative study in patients with spinal cord Injury

BackgroundNeurogenic bladder dysfunction is a major problem for spinal cord injury (SCI) patients not only due to the risk of serious complications but also because of the impact on quality of life. The main aim of this study is to compare the rate of urinary tract infection (UTI) associated with hydrophilic-coated catheters versus uncoated polyvinyl chloride (PVC) catheters among SCI patients presenting with functional neurogenic bladder sphincter disorders.MethodologyThis was a retrospective cohort study from 2005 to 2020 including adult male or female patients who have an SCI at least more than 1 month ago with neurogenic bladder dysfunction and were using intermittent catheterization (single-use hydrophilic-coated or the standard-of-care polyvinyl chloride uncoated standard catheters) at least 3 times a day to maintain bladder emptying.ResultsA total of 1000 patients were selected and recruited through a stratified random sampling technique with 467 (47.60%) patients in the uncoated catheter arm and 524 (52.60%) in the coated catheter groups. The three outcome measures, namely: symptomatic UTI, Bacteriuria, and pyuria were significantly higher in the group using uncoated polyvinyl chloride (PVC) catheters compared to hydrophilic-coated catheters at the rate of 79.60% vs.46.60%, 81.10% vs. 64.69, and 53.57% versus 41.79% respectively. Males, elder patients, longer duration, and severity of SCI were associated with increased risk of symptomatic UTI.ConclusionsThe results indicate a beneficial effect regarding clinical UTI when using hydrophilic-coated catheters in terms of fewer cases of symptomatic UTI. Bacteriuria is inevitable in patients with long-term catheterization, however, treatment should not be started unless the clinical symptoms exist. More attention should be given to the high-risk group for symptomatic UTIs.

Recording of chest leads via mobile ECG and quantitative correlation with Wilson leads in a patient with monomorphic PVCs

Abstract Introduction Mobile ECGs using handy smartphone-based devices such as the KardiaMobile (AliveCor) are increasingly used as diagnostic tool for arrhythmias. They can be especially useful in cases of non-permanent arrhythmia. However, they were designed to record limb leads and few experience exists with the recording of modified chest leads. However chest leads provide important diagnostic information in many forms of arrhythmias including premature ventricular contractions (PVCs). We hypothesized that chest lead recordings using the 6-lead enabled KardiaMobile 6L device in a novel way would closely resemble the Wilson chest leads. Methods A patient with monomorphic idiopathic PVCs was identified. A standard 12- lead ECG was then taken in a supine position, and the exact same electrode positions were then used to record a mobile ECG in the supine position in the following manner: right finger and left finger positioned at the right and left sensor of the KardiaMobile 6L device respectively; back sensor positioned on the chest wall at the former positions of the chest electrodes, in a sequential manner (figure 1). The QRS morphologies of the 12-lead ECG Wilson leads and the reconstructed chest-leads with the mobile device were then overlied using Adobe illustrator and photoshop. The 12-lead ECG was also compared to a second 12-lead ECG of the patient that had been taken on the day before. Results QRS-morphologies of the chest leads derived from the 12-lead ECG and mobile ECG device resembled closely considering both regularly conducted beats and PVCs (figure 2 left and middle ECGs). Transition scores (TZ) of the sinus beats (3,5) and the PVCs (4) were identical. Overlaying two representative QRS-complexes of leads V1-6 of the Wilson leads and the mobile tracings showed a mean correlation of 73% for sinus beats and 78% for PVCs. In comparison, correlation of the QRS-complexes between the two 12-lead ECGs taken on consecutive days was 60% and 68% respectively (figure 2 left and right ECGs). Conclusion QRS-morphologies of the chest-leads taken with the KardiaMobile closely resembled the Wilson leads of the 12-lead ECG, and correlated better than did another 12-lead ECG that was taken the day before. The techniques could be useful for self-recording of arrhythmias including PVCs by patients to guide clinical decision-making in cases where no 12-lead ECG can be achieved due to intermittent arrhythmia occurrence.

Research on pressure pulsation characteristics of a pump-turbine in pump mode with rotating stall: Focus on the broadband frequency

To investigate the adverse effects of rotating stalls on the pressure pulsation characteristics of a pump-turbine in pump mode, an unsteady numerical simulation was carried out by applying the partially averaged Navier–Stokes turbulence model. The numerical methods were carefully verified, and the onset flow rate of the hump at the performance curve and heads were in good agreement with the experimental data. The rotating stall appeared in the guide vane when the flow rate ranged from 0.514 to 0.887 times the best efficiency point (QBEP), with a frequency of 11.7% times the rotational frequency. In the period of a rotating stall, a sudden intensive pressure pulsation in the guide vane channel was observed and named as the component of the broadband frequency, and its corresponding flow mechanism was explained as the vortex evolution between the adjacent guide vane blades based on the dynamic mode decomposition technology. There were three distinct characteristics of broadband frequency: (i) intermittent occurrence when the rotating stall cell propagated to the current flow channel, (ii) a wide range of the frequency varying with flow rate, (iii) a considerable amplitude, e.g., reaching 21.1%–42.2% times that of the rotating stall frequency. In addition, both the frequency range and amplitude of the broadband frequency gradually decreased as the flow rate increased to 0.887QBEP. This study clarified the internal flow mechanism and frequency behaviors of a sudden intensive pressure pulsation if a rotating stall occurred, which was important to assess the stability of pump-turbine units.

English as a foreign language teachers' burnout: The predicator powers of self-efficacy and well-being

Educators have recently garnered significant focus for the crucial role they play, particularly concerning their emotions. These emotions have the potential to either boost their progress in their profession or hinder their progress, like burnout which may trigger or intensify poor mental health and quit the job. Burnout arises from the intermittent occurrence of emotional distress among English as a foreign language (EFL) educators as they fulfill their professional duties. To shed more light on the issue, it is fundamental to contemplate the teacher's belief in their capabilities, known as self-efficacy, which can reduce the probability of burnout and prevent work-related stress while also promoting beneficial results. Moreover, it has been evidenced that the vital role of educators' well-being is prominent in this procedure. Therefore, the importance of these two constructs concerning the impact they have on teacher burnout was taken into consideration in this study. To achieve this objective, a group of 403 English educators participated in the measurement of the concepts being studied. To scrutinize the causal connections between the variables, a Structural Equation Modeling (SEM) approach was employed. The study showed that teachers' efficacy in their ability to perform their job effectively was responsible for explaining 82 % of changes in burnout, while their level of well-being played a role in accounting for 42 % of changes in teachers' burnout levels. The data disclosed that while every factor independently contributed to burnout, the self-efficacy of the teachers held greater influence as a predictor of burnout in comparison to their well-being. Ultimately, particular academic suggestions are specified.

Experiments on the evolution process of intermittent air-entraining vortices and its influencing factors

Surface vortices are a common hydraulic phenomenon at water intakes that adversely affect safe engineering operations. The complexity of vortex motion, the diversity of influencing factors, and the limitations of research methods make the formation and development mechanisms of vortices unclear. Some analytical and experimental studies on intermittent air-entraining vortices occurring at the horizontal circular intake have been conducted to explore the mechanism of the dynamic characteristics of vortices. Based on experimental observations, the morphologies and dynamic characteristics of intermittent air-entraining vortices at different moments during the entire evolution process were studied, and the velocity field in the vortices was measured using PIV. The evolution processes of intermittent air-entraining vortices comprised inception, rapid development, stability, decay and regeneration, and the collapse and disappearance stages. The tangential velocity, kinetic energy, and vorticity increased over time, reached a maximum, and subsequently decreased. When they decrease to a certain value, they begin to increase before decreasing owing to the decay and regeneration stages. Additionally, we introduced the frequency of intermittent air-entraining vortex occurrence (P) to analyse the direct effect of the Froude number, intake submergence, and rear wall on the occurrence of air-entraining vortices. Based on the analysis of the test results, the effect of intake submergence on P was more significant than that of the intake Froude number in terms of flow conditions. By considering the effects of the flow conditions and rear wall, a method for predicting the possibility of the occurrence of intermittent air-entraining vortices was proposed.

An insight into the severe slugging characteristics in a catenary flexible riser

This paper reports the experimental results of the severe slugging (SS) flow characteristics in a downward inclined pipeline-catenary flexible riser system. The non-intrusive optical measurement with high-speed cameras was employed to capture the evolution of liquid slugs and the gas–liquid interface. Five SS patterns are identified in the considered flow velocity range. There are two kinds of severe slugging I (SSI-1 and SSI-2) with the essential difference in the occurrence of the fast blockage stage before the slug formation (SF) stage. The severe slugging II (SSII) is characterized with the longest liquid slug less than a riser length and the absence of slug production stage. The liquid slug is further shortened in severe slugging III (SSIII), exhibiting local liquid fallback and accumulation of multiple slugs in the riser. The severe slugging transition (SST) occurs due to the switching between the SSI-1 and SSII. The flow regime partition is plotted in the vsl (liquid superficial velocity)–vsg (gas superficial velocity) diagram, presenting alteration as the inclination angle of upstream pipeline varies. Generally, the SSI is easier to form at a higher inclination angle. The intermittent occurrence of hydrodynamic slug in the upstream pipeline in the SF stage contributes to the appearance of SSI-2 to SST. The SS cycle has approximately a negative exponent relation with vsg, while the riser base pressure changes exponentially with the increase in vsl.

Cross-Regional Pollination Behavior of Trichoplusia ni between China and the Indo-China Peninsula.

Noctuid moths, a group of "non-bee" pollinators, are essential but frequently underappreciated. To elucidate their roles in cross-regional pollination, this study selected the agriculturally significant species, cabbage looper (CL) Trichoplusia ni, as a representative model. From 2017 to 2021, this study was conducted on Yongxing Island, situated at the center of the South China Sea. We investigated the flower-visiting activities of CL, including its occurrence, potential host species, and geographic distribution in the surrounding areas of the South China Sea. First, the potential transoceanic migratory behavior and regional distribution of CL were systematically monitored through a comprehensive integration of the data obtained from a searchlight trap. The transoceanic migratory behavior of CL was characterized by intermittent occurrence, with the major migratory periods and the peak outbreak yearly. Furthermore, trajectory analysis confirmed the ability of CL to engage in periodic, round-trip, migratory flights between Southeast Asian countries and China. More importantly, an observation of pollen on the body surface demonstrated that 95.59% (130/136) of the migrating individuals carried pollen. The proboscis and compound eyes were identified as the primary pollen-carrying parts, with no observable gender-based differences in pollen-carrying rates. Further, identifying the pollen carried by CL using morphological and molecular methods revealed a diverse range of pollen types from at least 17 plant families and 31 species. Notably, CL predominantly visited eudicot and herbaceous plants. In conclusion, this pioneering study has not only revealed the long-distance migration activities of these noctuid moths in the East Asian region but also provided direct evidence supporting their role as potential pollinators. These findings offer a critical theoretical basis to guide the development of scientific management strategies.

Effects of heatwave events on the seagrass-dwelling crustacean Pandalus latirostris in a subarctic lagoon

Heatwaves often cause mass mortality of organisms in seagrass areas, and they eventually alter some ecological functions of seagrass ecosystems. In subarctic regions, however, the effects of heatwaves on seagrass areas are still unclear. In a subarctic lagoon of northern Japan, we examined the effects of heatwaves on the Hokkai shrimp, Pandalus latirostris, a commercially exploited species distributed in seagrass areas of northern Japan and eastern Russia. A long-term survey of the surface water temperature in the lagoon clarified a gradual increase in the frequency and intensity of heatwave events since 1999. Surveys of the water temperature at a seagrass area in the lagoon during summer have also demonstrated that the maximum water temperature had been exceeding 25 °C, unusually high for this location, regardless of water depth. These results indicate that the effects of heatwaves in seagrass areas in a subarctic region had become as severe as those in tropical and temperate regions. We also experimentally evaluated the effects of this unusually high water temperature (25 °C) on the survival of P. latirostris by changing the length of exposure time. Some individuals suffered damage to their intestinal mucosal structure after exposure for 12 h or longer, and all individuals died after exposure for 120 h. Our results suggest that heatwaves possibly cause mass mortality in P. latirostris in the following sequence: heat stress, damage to the intestinal epithelial mucosal structure, degradation of nutrient absorption and immunological function of the intestine, energy deficiency and disease infection, and finally mortality. This study, conducted in subarctic closed waters, concludes that it is essential to become familiar with not only trends in heatwaves but also the intermittent occurrence of unusually high water temperature in seagrass areas in order to better understand the process of mortality of organisms that inhabit these ecosystems.

Use of Nonofficial Intermittent Waterfall Occurrence Data for the Validation of an Infiltration Model for Volcanic Jeju Island, Korea

This study attempts to validate an infiltration model, the Soil Conservation Service–Curve Number (SCS–CN) method, using the nonofficial intermittent occurrence data of Eongtto Falls on Jeju Island, Korea. Simply due to the limited official continuous runoff data concerning Jeju Island, the validation of a newly set SCS-CN method for Jeju Island was practically impossible. Instead, this study tries to use nonofficial data for this purpose. This study focuses on the intermittent occurrence of Eongtto Falls, which is one of the most famous tourist attractions on the island. Various records of Eongtto Falls can be collected from newspapers, personal homepages, and various social networking services. The SCS-CN method is, in this study, used to check if effective rainfall occurs or not. In fact, this approach is quite effective on Jeju Island, as most streams are fully dry during non-rain periods. Evaluation of the SCS-CN method is based on the analysis of a contingency table, which measures the consistency of the occurrence of effective rainfall events and waterfall records. Additionally, to quantify the results of the contingency table, some measures such as accuracy, hit ratio, and false alarm ratio are used. This analysis is carried out using all the rainfall events from 2011 to 2019, and the derived results confirm that the newly set SCS-CN method is far better than the conventional one used thus far.

Different types of Status Epilepticus may lead to similar hippocampal epileptogenesis processes

About 1–2% of people worldwide suffer from epilepsy, which is characterized by unpredictable and intermittent seizure occurrence. Despite the fact that the exact origin of temporal lobe epilepsy is frequently unknown, it is frequently linked to an early triggering insult like brain damage, tumors, or Status Epilepticus (SE). We used an experimental approach consisting of electrical stimulation of the amygdaloid complex to induce two behaviorally and structurally distinct SE states: Type I (fully convulsive), with more severe seizure behaviors and more extensive brain damage, and Type II (partial convulsive), with less severe seizure behaviors and brain damage. Our goal was to better understand how the various types of SE impact the hippocampus leading to the development of epilepsy. Despite clear variations between the two behaviors in terms of neurodegeneration, study of neurogenesis revealed a comparable rise in the number of Ki-67 + cells and an increase in Doublecortin (DCX) in both kinds of SE.

Anthropogenic climate change exacerbates the risk of successive flood-heat extremes: Multi-model global projections based on the Inter-Sectoral Impact Model Intercomparison Project

The successive flood-heat extreme (SFHE) event, which threatens the securities of human health, economy, and building environment, has attracted extensive research attention recently. However, the potential changes in SFHE characteristics and the global population exposure to SFHE under anthropogenic warming remain unclear. Here, we present a global-scale evaluation of the projected changes and uncertainties in SFHE characteristics (frequency, intensity, duration, land exposure) and population exposure under the Representative Concentration Pathway (RCP) 2.6 and 6.0 scenarios, based on the multi-model ensembles (five global water models forced by four global climate models) within the Inter-Sectoral Impact Model Intercomparison Project 2b framework. The results reveal that, relative to the 1970–1999 baseline period, the SFHE frequency is projected to increase nearly globally by the end of this century, especially in the Qinghai-Tibet Plateau (>20 events/30-year) and the tropical regions (e.g., northern South America, central Africa, and southeastern Asia, >15 events/30-year). The projected higher SFHE frequency is generally accompanied by a larger model uncertainty. By the end of this century, the SFHE land exposure is expected to increase by 12 % (20 %) under RCP2.6 (RCP6.0), and the intervals between flood and heatwave in SFHE tend to decrease by up to 3 days under both RCPs, implying the more intermittent SFHE occurrence under future warming. The SFHE events will lead to the higher population exposure in the Indian Peninsula and central Africa (<10 million person-days) and eastern Asia (<5 million person-days) due to the higher population density and the longer SFHE duration. Partial correlation analysis indicates that the contribution of flood to the SFHE frequency is greater than that of heatwave for most global regions, but the SFHE frequency is dominated by the heatwave in northern North America and northern Asia.

Epidemiological Transition in Iran: The Rise and Fall of Epidemics in Iran After Islam to Before the Islamic Revolution

Background and aims: The lack of reliable data on mortality in Iran until the last few decades has caused the early stages of the epidemiological transition to remain unknown. As such, the current study was an attempt to examine the stages and timing of the epidemiological transition in Iran in a historical effort. Methods: This study is descriptive-analytical, and its data and information have been collected using the library method. Results: The historical course of the emergence of epidemics in Iran after Islam to before the Islamic Revolution is divided into four periods: (1) The period after Islam to the Safavid period (650-1501 AD): The era of plague and famine, (2) Safavid to Qajar period (1501-1796 AD): The era of continued widespread outbreaks and intermittent occurrence of plague, (3) Qajar period (1796-1925 AD): The era of subsidence of the plague and widespread cholera, and finally (4) Pahlavi period (1925-1979 AD): The era of the decline of epidemic diseases. Conclusion: The continuous and substantial reduction in deaths led simultaneously to a reduction in the incidence and scope of epidemics and an increase in chronic diseases, and this process is expected to accelerate in the future.

Geochemistry of Layered Ultramafic Rocks in J.C. Pura Schist Belt, Dharwar Craton, Karnataka, India

The Jayachamarajapura schist belt in western Dharwar craton, southern India, is predominantly an ultramafics dominant terrain. These rocks have been extensively metamorphosed and altered to serpentinite. The komatiite nature of ultramafics is conspicuous. In most of the areas of the belt these ultramafics are massive in nature. However, some of the ultramafic units show layered nature. But, their outcrops are encompassed within the massive komatiitic bodies. These komatiitic ultramafics are predominantly Mg-rich in nature. The layered rocks are also Mg-rich, and their field setting and geochemistry suggest their intermittent occurrence as sills, during the differentiation of peridotitic magma. The layered rocks, which have been intensely serpentinisation show homogenous nature. They are almost wholly made of serpentine with occasional relics of pyroxene. Secondary carbonate mineral is often noticed. Their higher MgO content indicates Mg-rich ultramafic magmatism during Archaean orogeny.

MONITORING AND DETECTION OF WHEAT BLAST DISEASE CAUSED BY MAGNAPORTHE ORYZAE TRITICUM PATHOTYPE IN PUNJAB, PAKISTAN

The wheat blast caused by the Magnaporthe oryzae Triticum pathotype has become a serious threat to wheat production in Pakistan and India after its severe outbreak in Bangladesh in 2016 and intermittent occurrence since then. Thus, planned systemic surveillance of wheat crops in two phases in 2018–2019 and 2019–2020 began to determine the status of wheat blasts in Punjab, Pakistan. In the first phase, a survey of 160 wheat fields in districts in Punjab ensued for typical blast symptoms. The surveillance‟s second phase occurred after the threshing of the wheat crop, with composite grain samples collected from all over Punjab, then analyzed in the lab. The surveillance results indicated that all the wheat fields were free from the typical blast symptoms. Similarly, none of the analyzed samples showed the presence of wheat blast pathogens. Therefore, the study validates that this dreadful disease (blast) does not exist in Punjab, Pakistan. Hence, the reason to remain calm needs dissemination among the farming community and the training of technical agriculture extension staff for vigilance in the future for monitoring this disease in different agro-ecological zones of Punjab.

Surface circulation properties in the eastern Mediterranean emphasized using machine learning methods

Abstract. The eastern Mediterranean surface circulation is highly energetic and composed of structures interacting stochastically. However, some main features are still debated, and the behavior of some fine-scale dynamics and their role in shaping the general circulation is yet unknown. In the following paper, we use an unsupervised neural network clustering method to analyze the long-term variability of the different mesoscale structures. We decompose 26 years of altimetric data into clusters reflecting different circulation patterns of weak and strong flows with either strain or vortex-dominated velocities. The vortex-dominated cluster is more persistent in the western part of the basin, which is more active than the eastern part due to the strong flow along the coast, interacting with the extended bathymetry and engendering continuous instabilities. The cluster that reflects a weak flow dominated the middle of the basin, including the Mid-Mediterranean Jet (MMJ) pathway. However, the temporal analysis shows a frequent and intermittent occurrence of a strong flow in the middle of the basin, which could explain the previous contradictory assessment of MMJ existence using in-situ observations. Moreover, we prove that the Levantine Sea is becoming more and more energetic as the activity of the main mesoscale features is showing a positive trend.

Vortex Dislocation In The Near Wake Of A Cylinder With Span-Wise Variations In Diameter

We examined the evolution of three-dimensional vortex shedding patterns induced by spanwise variations of the cylinder diameter. Two distinct types of shedding patterns have identified through flow visualization: continuous (in-phase) oblique shedding where vortices shed with lower frequency stay attached to the vortices with higher frequency without any discontinuity or splitting and discontinuous (out-of-phase) shedding where the lower frequency vortices have no attachment to higher frequency vortices and vortex dislocation occurs. The dislocation seen in the flow is strongly influenced by the span wise irregularities. We observed a clear and strong in-phase spanwise vortex shedding for the three smooth cylinder configurations tested in the study. The tapered, bumps and steps configurations showed sections of strong coherent spanwise vortex shedding, and we identified hardly any coherent structures for the rib, sinusoidal, and helical configurations. Depending on the geometry and number of span wise irregularities, incoherent structures make difficult to determine the occurrence and location of vortex dislocations in the cylinder wake without a method that enables a reduction in the complexity. Here, we introduce a numerical approach that obtains the dominant structures of vortex shedding patterns by reducing the complexity in noisy data. The method maps the variations in the oblique shedding angle over time and provide quantitative conclusions on the intermittent occurrence and location of vortex dislocations in the 15000 snapshots taken for each of the different cylinder geometries regardless of turbulence.

Experimental investigations of hypersonic inlet unstart/restart process and hysteresis phenomenon caused by angle of attack

In this study, the unstart/restart process of a hypersonic inlet caused by the angle of attack (AOA) is experimentally performed at a Mach number of 5.0, and the unsteady flow characteristics during the test are investigated. The flow characteristics are simultaneously recorded using high-frequency pressure measurement and high-speed schlieren imaging. The results show that the inlet enters the unstarting state at AOA = 8.4° but restarts at AOA = 0.3°, exhibiting an obvious hysteresis phenomenon. During the unstart process, the forebody shock gradually approaches the body and then impinges on the inside of the cowl with the increasing angle of attack, indicating that the inlet works under an overrated mode. As the angle of attack increases further, the airflow chokes, and a high-pressure zone is first formed in the exit of the duct. Then, the high-pressure signal propagates upstream in the duct, leading to the emergence of an inlet unstart. When the inlet enters the unstarted pattern, a typical local unstarted flow field is formed. Low-amplitude oscillations occur in the internal contraction region, but further propagation to the isolator is weak. During the restart process, when the angle of attack decreases from 3.2° to 0.3°, two kinds of big buzz patterns, namely, intermittent high-amplitude oscillation and periodic high-amplitude oscillation, appear successively. The intermittent high-amplitude oscillation is characterized by the intermittent occurrence of a high-amplitude oscillation after the low-amplitude oscillations for a random length of time. In the periodic high-amplitude oscillation, the separation bubble is repeatedly disgorged and swallowed, resulting in a dominant fluctuation frequency in the entire duct. Furthermore, as the angle of attack decreases, the dominant frequency gradually rises from 280 Hz to 339 Hz. This work provides new insights into the flow evolutions and unsteady behaviors of hypersonic inlet unstart/restart owing to the AOA and provides potential applications on the detection and prediction of hypersonic inlet unstart/restart.

Economic resilience in an era of ‘systemic risk’: Insights from four key economic sectors in Sri Lanka

COVID-19 has showcased the systematic nature of risks. Its effects have spanned beyond the health sector causing severe economic disruptions. Sri Lanka's GDP contracted by 3.6% in 2020 from a 2.3% growth in 2019, reflecting the largest economic downturn recorded in the country's history. Although the COVID-19 pandemic has been largely perceived as unprecedented by most economic sectors and businesses functioning within them, pandemics are not a novel phenomenon given their intermittent occurrence in the past. This study aimed at examining the resilience of four key sectors in Sri Lanka during the COVID-19 pandemic, namely apparel, tourism, agriculture and construction. The study sought to identify the factors that have both enhanced and hindered their resilience during the pandemic and provide recommendations to strengthen their resilience for future pandemics and multi-hazard scenarios featuring pandemics. The study draws upon primary data gathered through four round table discussions carried out with a total of 30 key informants representing the selected sectors. The findings reveal that for economic resilience to be achieved within the selected economic sectors, resilience building measures should be undertaken at three levels: 1) orgaizational level; 2) sectoral level and 3) country level, while also recognising the need for consonance and congruence between measures taken at each level.

Transition, intermittency and phase interference effects in airfoil secondary tones and acoustic feedback loop

A large eddy simulation is performed to study secondary tones generated by a NACA0012 airfoil at angle of attack of $\alpha = 3^{\circ}$ with freestream Mach number of $M_{\infty} = 0.3$ and Reynolds number of $Re = 5 \times 10^4$ . Laminar separation bubbles are observed over the suction side and near the trailing edge, on the pressure side. Vortex shedding occurs aft of the suction side separation bubble, and vortex interaction results in merging or bursting such that coherent structures or turbulent packets are advected towards the trailing edge. This mechanism modulates the amplitude of the incident pressure signal, leading to different levels of noise emission. Despite the intermittent occurrence of laminar–turbulent transition, the noise spectrum depicts a main tone with multiple equidistant secondary tones. To understand the role of flow instabilities on the tones, the linearised Navier–Stokes equations are examined in their operator form through biglobal stability and resolvent analyses, and by time evolution of disturbances using a matrix-free method. These linear global analyses reveal amplification of disturbances over the suction side separation bubble. Spanwise-averaged pressure fluctuations elucidate aspects of the acoustic feedback loop mechanism in the nonlinear solutions. This feedback process is self-sustained by acoustic waves radiated from the trailing edge, which reach the most sensitive flow location near the leading edge, as identified by the resolvent analysis. Flow disturbances arising from secondary diffraction and phase interference among the most unstable frequencies computed in the eigenspectrum are shown to have an important role in the feedback loop.

In-Plane Strengthening of Unreinforced Masonry Walls by Glass Fiber-Reinforced Polyurea

Strengthening techniques have been employed in Korea to unreinforced masonry walls (UMWs) for several years to protect them from damage caused by the intermittent occurrence of earthquakes. Polyurea, which has a high tensile strength and elongation rate, can be utilized as a strengthening material to enhance the in-plane strength and ductility of UMWs. Glass fiber-reinforced polyurea (GFRPU) is a composite elastomer manufactured by progressively adding milled glass fiber to polyurea. The purpose of this study is to investigate the enhancement of the in-plane strength and ductility of UMWs using GFRPU, depending on the shape of the GFRPU coating on the wall. Four masonry wall specimens are tested with test variables of the number of strengthening sides and coating shapes. It is illustrated that the GFRPU reinforcement of masonry wall leads to enhanced load-carrying capacity, ductility, and energy absorption. An empirical formula to represent the degree of strengthening effected by GFRPU is proposed in this study. Doi: 10.28991/cej-2021-03091782 Full Text: PDF