Cyclic Variation Research Articles

Cobweb phenomenon in rubber market of Kerala

More than 90 percent of rubber produced in India is from Kerala. The state holds a dominant position both in area and production. But now a day farmers are looking at alternative crops or not tapping their rubber as prices have crashed due to lack of demand, imports and labour cost. The study revealed that during high priced season farmers in Kerala shifted from other plantation crops like cashew, coconut, etc. to rubber or they focus only in rubber production but in higher prices, seeks to benefit from higher prices. These results in surplus production, more than the demand, resulting in a price crash, often referred to as the ‘problem of plenty’. Seeing the low prices, farmers switch to different crops or produce less of the same crop, leading to lower than usual production for that particular crop. This increases the prices of crops, completing the cyclical variations in price and production reflects Cobweb phenomenon.

Measurement error prediction-based reliability assessment framework for electric metering devices under harsh natural environments

Reliability assessment for electric metering devices (EMDs), which includes environmental stress analysis, measurement error (ME) prediction, and reliability estimation, can be utilized for predictive instrument maintenance, especially under harsh environmental stresses. Nevertheless, the actual evaluation process is limited by data noise and the unavailability of future environmental inputs for the degradation model. To this end, we first extract the main environmental factors affecting ME and then fuse them using the weighted principal component analysis (WPCA) method to provide future environmental input values for the prediction model. Next, a bi-directional (BD) outlier detection method based on MCD robust analysis and the Thompson tau method is proposed to detect outliers from horizontal and longitudinal perspectives. Then, an ME prediction method called multi-stress fusion nonlinear degradation (MFND) is put forward, which considers the cyclic variation of ME over time and the effect of environmental stresses on ME. Real-world datasets from a high-dry-hot area manifest that our proposed BD-based MFND reliability assessment framework enjoys pleasurable prediction performance. Compared to some well- known methods, our framework excels in outlier detection and ME prediction.

Controllable release of Cu ions contributes to the enhanced environmentally-friendly performance of antifouling Cu-bearing stainless steel coating prepared using high-velocity air fuel

Organic antifouling coatings represent an economical and efficient solution for addressing the marine biofouling. However, their application is constrained by issues of durability and toxicity. Therefore, this study has developed a metal-based antifouling coating by utilizing pre-alloyed copper-bearing stainless steel (Cu-bearing SS) powder in conjunction with high-velocity air fuel (HVAF) technology, aiming to achieve an environmentally-friendly and long-lasting antifouling coating. Compared to the self-polishing copolymer (SPC) coating, the adhesion strength of Cu-bearing SS coating increased to 69.0 MPa, which is approximately a 33-fold increase. The coating also exhibited enhanced wear resistance, the width and depth of the wear track for the Cu-bearing SS coating decreased 42.9 % and 81.0 %, respectively. Furthermore, the coating still demonstrated strong inhibitory effects on typical fouling microorganisms and algae adhesion due to Cu ions release process environmentally-friendly. The electrochemical techniques coupling with surface morphology observations were used to elucidate the antifouling mechanism. The variation trend of coating corrosion current was consistent with the release process of Cu ions, which was directly related to the evolution of the coating surface morphology. The three-stage change in the surface morphology of the 304 L-Cu SS coating contributes to the formation of a cyclic variation trend process of Cu ions. The evolution of surface morphology, accompanied by the controlled release process of Cu ions, had become a distinctive feature of antifouling properties for a metal-based coating.

Cyclic variations of the structure and energetics of solar magnetic fields

ABSTRACT The solar cycle is a complex phenomenon, a comprehensive understanding of which requires the study of various tracers. Here, we consider the solar cycle as manifested in the harmonics of the solar large-scale surface magnetic field, including zonal, sectorial, and tesseral harmonics, divided into odd and even relative to the solar equator. In addition to considering the amplitudes of the harmonics, we analyse their contribution to the magnetic energy. It turns out that the relative contribution of different types of harmonics to the magnetic energy is virtually independent of the cycle height. We identify different phases of the activity cycle using harmonics of different symmetries. A possible way to incorporate the obtained result into the solar dynamo theory is proposed.

Stellar Cycle and Evolution of Polar Spots in an M+WD Binary

Stellar activity cycles reveal continuous relaxation and induction of magnetic fields. The activity cycle is typically traced through the observation of cyclic variations in total brightness or Ca H&K emission flux of stars, as well as cyclic variations in the orbital periods of binary systems. In this work, we report the identification of a semidetached binary system (TIC 16320250) consisting of a white dwarf (0.67 M ⊙) and an active M dwarf (0.56 M ⊙). The long-term multiband optical light curves spanning twenty years revealed three repeated patterns, suggestive of a possible activity cycle of about 10 years of the M dwarf. Light-curve fitting indicates the repeated variation is caused by the evolution, particularly the motion, of polar spots. The significant Ca H&K, Hα, ultra-violet, and X-ray emissions imply that the M dwarf is one of the most magnetically active stars. We propose that in the era of large time-domain photometric sky surveys (e.g., ASAS-SN, Zwicky Transient Facility, LSST, Sitian), long-term light-curve modeling can be a valuable tool for tracing and revealing stellar activity cycle, especially for stars in binary systems.

Aspects of the combustion variability analysis at an automotive engine fuelled with hydrogen

Over the last decades, the use of the alternative fuels was one of the main research activities for specialists in the field of internal combustion engines. The development of the modern automotive engines is constantly challenged by the more severe emission legislation. The engine emissions levels and the fuel efficiency are directly influenced by the engine operation, reproduction of the combustion phases from one cycle to other, cyclic dispersion during combustion process being important. In general, the use of alternative fuels in internal combustion engines provides an improvement of the energetic and pollution performance, or just a slight improvement of them, but the study of the combustion process must be completed with aspects regarding the cyclic variability. In particular, using this alternative fuel, a study of cyclic variation of the combustion process would be necessary in order to establish if the normal operation of the engine can be ensured. The paper presents some aspects of the analysis of the cyclic variability at a spark ignition engine fuelled with gasoline and hydrogen. During the engine operation at the regime of 2500 rev/min speed and 55% engine load, a number of 250 consecutive combustion cycles was recorded for classic fuel use and for hydrogen use. The coefficient of cyclic variation (CCV) or the coefficient of variation (COV) is determined for different combustion parameters such as maximum pressure, maximum pressure rise rate and mass fraction burned, defined by angles at which the conventional fractions of 10%, 50% and 90% of the heat of reaction is released. Thus, the values of the COV for maximum pressure (COV)pmax, maximum pressure rise rate (COV)dp/dα, angles of 10, 50 and 90% heat release as (COV)10%, (COV)50% and (COV)90% were calculated and compared with the admissible limit of 10%. The combustion variability analysis establishes the limits of the normal operation of the spark ignition engine fuelled with gasoline and hydrogen compared with the classic fuelling method.

Examining the Effect of Freezing Temperatures on the Survival Rate of Micro-Encapsulated Probiotic Lactobacillus acidophilus LA5 Using the Flash Freeze-Drying (FFD) Strategy.

This work proposes a novel drying method suitable for probiotic bacteria, called flash freeze-drying (FFD), which consists of a cyclic variation in pressure (up-down) in a very short time and is applied during primary drying. The effects of three FFD temperatures (-25 °C, -15 °C, and -3 °C) on the bacterial survival and water activity of Lactobacillus acidophilus LA5 (LA), previously microencapsulated with calcium alginate and chitosan, were evaluated. The total process time was 900 min, which is 68.75% less than the usual freeze-drying (FD) time of 2880 min. After FFD, LA treated at -25 °C reached a cell viability of 89.94%, which is 2.74% higher than that obtained by FD, as well as a water activity of 0.0522, which is 55% significantly lower than that observed using FD. Likewise, this freezing temperature showed 64.72% cell viability at the end of storage (28 days/20 °C/34% relative humidity). With the experimental data, a useful mathematical model was developed to obtain the optimal FFD operating parameters to achieve the target water content in the final drying.

Plethysmography variation index versus pulse pressure variation as an indicator of fluid responsiveness in colorectal surgeries during immediate postoperative period

ABSTRACT Background During major abdominal surgery, goal-directed fluid therapy may lessen postoperative morbidity. It has been demonstrated that the Plethysmography Variability Index (PVI), which is generated from the pulse oximeter waveform, can predict fluid responsiveness in a variety of surgical settings. Pulse pressure variation (PPV), one of the indicators of fluid responsiveness, has received the most research attention and clinical application of all the indicators. Through arterial cannulation, primarily the radial artery, pulse pressure fluctuation is recorded. The cyclic variations in intrathoracic pressure have less of an immediate impact on pulse pressure than they do on systolic pressure. In this study, sedated, intubated, mechanically ventilated patients admitted for postoperative resuscitation in our surgical ICU following colorectal surgeries had their fluid responsiveness assessed using the Plethysmography Variation Index (PVI) and the Pulse Pressure Variation (PPV) to compare their effectiveness and reliability.

Piezoelectric rubber sheet sensor: a promising tool for home sleep apnea testing

PurposeThis study aimed to develop an unobtrusive method for home sleep apnea testing (HSAT) utilizing micromotion signals obtained by a piezoelectric rubber sheet sensor.MethodsAlgorithms were designated to extract respiratory and ballistocardiogram components from micromotion signals and to detect respiratory events as the characteristic separation of the fast envelope of the respiration component from the slow envelope. In 78 adults with diagnosed or suspected sleep apnea, micromotion signal was recorded with a piezoelectric rubber sheet sensor placed beneath the bedsheet during polysomnography. In a half of the subjects, the algorithms were optimized to calculate respiratory event index (REI), estimating apnea–hypopnea index (AHI). In the other half of subjects, the performance of REI in classifying sleep apnea severity was evaluated. Additionally, the predictive value of the frequency of cyclic variation in heart rate (Fcv) obtained from the ballistocardiogram was assessed.ResultsIn the training group, the optimized REI showed a strong correlation with the AHI (r = 0.93). Using the optimal cutoff of REI ≥ 14/h, subjects with an AHI ≥ 15 were identified with 77.8% sensitivity and 90.5% specificity. When applying this REI to the test group, it correlated closely with the AHI (r = 0.92) and identified subjects with an AHI ≥ 15 with 87.5% sensitivity and 91.3% specificity. While Fcv showed a modest correlation with AHI (r = 0.46 and 0.66 in the training and test groups), it lacked independent predictive power for AHI.ConclusionThe analysis of respiratory component of micromotion using piezoelectric rubber sheet sensors presents a promising approach for HSAT, providing a practical and effective means of estimating sleep apnea severity.

GENDER DIFFERENCES IN SLEEP DURING AGING: A NARRATIVE REVIEW

Sleep is a fundamental biological need for rest, maintenance and restoration of physical and mental well-being. Irregular sleep causes changes in the circadian cycle and can lead to changes in physiological processes. Furthermore, it is different between men and women. Therefore, the objective of this research is to carry out a narrative review on the topics, sleep, aging and the difference between sleep in relation to gender. The literature points out that there are differences in sleep between women and men. Women present complaints regarding sleep, such as insomnia, due to the physiological and cyclical variation of their organism. Men, on the other hand, report more problems with their sleep due to respiratory problems, such as apnea, and excessive daytime sleepiness. There are few studies on the topic nowadays, so it would be interesting to study more about the impact of these differences during aging

Estrogen-mediated individual differences in female rat voluntary running behavior.

Regular exercise has numerous health benefits, but the human population displays significant variability in exercise participation. Rodent models, such as voluntary wheel running (VWR) in rats, can provide insight into the underlying mechanisms of exercise behavior and its regulation. In this study, we focused on the role of estrogen on VWR in female rats. Female rats run more than males, and we aimed to determine to what extent running levels in females were regulated by estrogen signaling. The running behavior of rats (duration, speed, and total distance run) was measured under normal physiological conditions, ovariectomy (OVX), and estrogen replacement in an OVX background. Results show cyclic variations in running linked to the estrous cycle. Ovariectomy markedly reduced running and eliminated the cyclic pattern. Estrogen replacement through estradiol benzoate (EB) injections and osmotic minipumps reinstated running activity to pre-OVX levels and restored the cyclic pattern. Importantly, individual differences and ranking are preserved such that high versus low runners before OVX remain high and low runners after treatment. Further analysis revealed that individual variation in running distance was primarily caused by rats running different speeds, but rats also varied in running duration. However, it is noteworthy that this model also displays features distinct from estrogen-driven running behavior under physiological conditions, notably a delayed onset and a broader duration of running activity. Collectively, this estrogen causality VWR model presents a unique opportunity to investigate sex-specific mechanisms that control voluntary physical activity.NEW & NOTEWORTHY This study investigates estrogen's role in voluntary wheel running (VWR) behavior in female rats. Female rats exhibit greater running than males, with estrogen signaling regulating this activity. The estrous cycle influences running, whereas ovariectomy reduces it, and estrogen replacement restores it, maintaining individual differences under all conditions. Both running speed and duration contribute to VWR variations. These findings emphasize individual estrogen regulation in female exercise and provide an estrogen replacement animal model for investigating neurobiological underpinnings that drive voluntary exercise behavior.

Multiwavelength research of the cyclic variability of symbiotic nova RT Ser

Multiwavelength research of the cyclic variability of symbiotic nova RT Ser

Metamaterials with modulated coefficient of thermal expansion and ultra-low thermal stress

Mechanical Metamaterials, which integrate multi-material systems, possess the exclusive capability to modulate the coefficient of thermal expansion (CTE). However, the thermal stress induced by the uncoordinated deformation of multi-material seriously restricts their engineering applications under cyclic and extreme temperature variations. Here, an innovative Zigzag Connection (ZC) metamaterial is originally developed to integrate the modulated CTE and ultra-low thermal stress, in contrast to the End-to-end Connection (EC) and Side-to-side Connection (SC) metamaterials reported in the literature. The mechanism and theoretical analysis of the CTE and thermal stress are established and validated through numerical simulations. It is revealed that the EC and SC metamaterials consistently generate the high thermal stress far beyond the yield strength, while the newly designed ZC metamaterial simultaneously exhibits the modulated CTE and ultra-low thermal stress. Moreover, an Ashby plot of CTE versus thermal stress is illustrated, and the concept of temperature variation tolerance is defined to guide the comprehensive design of these metamaterials. The ZC metamaterial shows a higher temperature variation tolerance within compared with the EC and SC metamaterials. Overall, the ZC metamaterial emerges as a solution for the inherent conflict between the modulate CTE and thermal stress, highlighting its obvious superiority of applications under high-temperature environments.

Fearing the Fed: How wall street reads main street

We provide strong evidence of a countercyclical sensitivity of the stock market to major macroeconomic announcements. The most notable cyclical variation takes place within expansions: sensitivity is largest early in an expansion and essentially zero late in an expansion. By exploiting the comovement pattern between stocks and bonds around announcements, we show that the stock market sensitivity is large when the cash flow component of news is least offset by news about future risk-free rates. Observed fluctuations in stock sensitivities can be attributed to shifting perceptions of monetary policy responsiveness.

The association of circadian rhythms with academic, physical, and cognitive performance: A systematic review

Introduction. Biological cycles exist across diverse time spans. Circadian rhythms are the most thoroughly examined and significantly influence individuals. These rhythms in physiological measures are affected by cyclical variations in human actions and surroundings over a 24-hour duration. Aim. The present research aims to analyse the association of biorhythm factors with performance in students considering research in the field of chronobiology in relation to the educational field. Research methodology and methods. The present systematic review summarises 34 records treating sleep quality, lifestyle, and circadian preferences in their association with the academic, physical, and cognitive performance of students during their daily life; using a PRISMA model. Results. The current review paper has cited numerous studies that confirm the significant impact of sleep and circadian preference on a student’s academic, psychomotor, and cognitive performance. These two factors play a crucial role in the rhythmicity of a student’s life. Scientific novelty. This study introduces a novel interdisciplinary method that applies findings from the study of biological rhythms to education, revealing how these rhythms affect student learning and performance. By merging chronobiology with educational theory, it opens new research paths and enhances our understanding of the relationship between students’ circadian rhythms and their academic, cognitive and physical results, representing a significant progression in how the field of education is linked with chronopsychology. Practical significance. Educational professionals can use the results obtained to gain a deeper insight into how chronobiological factors may affect student performance, thereby enhancing their comprehension of student productivity and potentially identifying more efficient ways to improve it.

A Short Period Sraffa-Keynes Model for the Evaluation of Monetary Policy

ABSTRACT This paper develops a short period, one sector, Sraffa-Keynes model that can be used for the evaluation of various recommendations outlined in the Post Keynesian monetary policy literature. The model is characterised by the principle of effective demand, Sraffa or target-return pricing (which integrates the determination of key distributive variables and allows for short run cyclical variation in prices), conflict inflation, endogenous money and a basic approach to monetary policy in the Smithin–Wray tradition of fixing the policy rate to achieve low or specified rates of unemployment. The model is calibrated to the Australian economy and subjected to two standard macroeconomic shocks, a demand shock and a cost shock. After each shock, the economy returns to long period equilibrium characterised by the achievement of the target rate of return, desired capacity utilisation and Sraffian prices of production. Active monetary policy that targets employment, reduces the depth and duration of recessions in this model compared to a ‘park-it’ approach but at the cost of increased volatility in income distribution. Flexible prices (where firms respond to the additional costs of running the capital stock at other than full capacity) are shown to have similar effects to monetary policy.

MODELING THE RELATIONSHIP OF STRUCTURAL SHIFTS IN INDUSTRY AND THE IMPACT OF EXPORTS OF HIGH-TECH PRODUCTS ON THE DOMESTIC MARKETS OF THE UNITED STATES AND CHINA

The relevance of identifying the relationship between structural shifts in industry and the impact of exports of high-tech products on the price and cost parameters of the domestic markets of the leading countries of the modern world economy is caused by the need for a comprehensive study of uncertainty and imbalance under the influence of structural-cyclical factors of market development. The development of relevant models that contribute to the identification and empirical justification of the desired relationship from the standpoint of partial equilibrium in the external and internal markets of the United States and China has both theoretical and applied significance in the context of the reindustrial turn based on convergent technologies. The purpose of modeling is to establish and substantiate the possible relationship between structural shifts in the industry and the impact of exports of high-tech products on the domestic markets of the United States and China. On the basis of previous experience, a complex econometric model has been developed, including computational-mathematical and regression-functional tools that allow analyzing dependent and factor variables within two successive cyclical waves of the current century. The interrelations of structural shifts in industry and the impact of exports of high-tech products on the domestic markets of the leading countries of the world industrial and technological rivalry – the USA and China – have been identified and substantiated. The modeling performed allows not only to identify comparative advantages at the country, national-economic level in terms of the impact of convergent technologies on the structure of production and exports in various cyclical variations, but also reflects the utility function for consumers of high-tech products in the domestic market of the United States and China. The dependences revealed as a result of modeling not only empirically, but also conceptually link the competition between manufacturers of high-tech products of each of the countries, alternately correlated as an exporting country and a global exporting country of the corresponding commodity groups. This creates a unique opportunity to show the multi-level relationship in the system "structural shifts - exports - domestic market" by comparing the dependent and factor variables of econometric and regression calculations. The results obtained correspond to the current practice in the world economy, revealing the desired relationships more consistently than when analyzing the competition of specific companies operating in the oligopolistic markets of the compared exporting countries.

Thermally induced mechanical interactions of energy pile groups subjected to cyclic nonsymmetrical thermal loading

Prior to this study, the long-term thermally-induced mechanical interactions of cyclic nonsymmetrical thermally loaded energy pile groups in soft clay have not been systematically elucidated, particularly with a limited understanding of the interactions among operating and non-operating energy piles, soil, and caps. Observing such a challenge, this paper presents a three-dimensional (3D) thermomechanical finite-element model (FEM), which considers the thermal-dependent behavior at the pile-soil interface and is validated using typical centrifuge tests reported in the literature. Special attention is given to the influence of soil-pile thermal expansion coefficient ratio, pile-soil stiffness ratio, and slab-soil stiffness ratio on the abovementioned interaction. The results indicate that a larger soil-pile thermal expansion coefficient ratio intensifies the interaction between energy piles and the surrounding soil, causing cyclic variations in thermally mobilized friction. With increasing pile-soil stiffness ratios, the differential thermomechanical responses among different piles within a group are enhanced because the toe and shaft resistances mobilized by the cap through nonoperating energy piles are weakened in the interaction process among energy piles, nonoperating energy piles, and the cap. Moreover, the increase in the slab-soil stiffness ratio exacerbates this interaction, strengthening the integrity of the pile groups.

Discriminating the leaves of Ocimum sanctum Linn. conferring to their age by gas chromatographic fingerprint analysis assisted with multivariate analysis

Ocimum species is having massive variations in their chemical composition that includes day time, terrestrial and cyclical variation according to the season etc. In this study, variation in overall essential oil constituents among matured, intermediate and young leaf samples of O. sanctum was studied. The leaf samples according to their age- matured, intermediate and young leaves were collected from three different plants at 11 a.m. each. Extract of collected leaf samples were then scrutinized using gas chromatographic technique having flame ionization detector (GC-FID). Result reveals that the noteworthy variance was observed in overall essential oil constituents of the leaf samples according to their age. The Average chromatographic fingerprint data of triplicate run for different leaf samples were then treated to multivariate methods such as hierarchical cluster analysis and principal component analysis. In this study, instead of considering one or two biomarkers, we have exasperated to obtain as many constituents in chloroform extracts of chosen leaf samples. Scree plot reveals that nine components were responsible for the whole variation. Score plot and dendogram efficiently discriminated all the three leaf types according to their age in different clusters. The outcome as an inference was, O. sanctum leaves according to their age exhibit variation in its chemical composition and developed tool can be used for routine quality control.

Modeling hydrogen–diesel dual direct injection combustion with FGM and transported PDF

This work extends the transported probability density function (PDF) method to model hydrogen–diesel dual direct injection (H2DDI) combustion, where a H2 jet is ignited by a small pilot diesel jet flame. The work is motivated by previous H2DDI engine tests where stable compression ignition engine operation was reported with up to 90 % H2 supply by energy share. To help explain this high performance and provide a tool to help further engine optimization, the Eulerian Monte Carlo Fields (EMCF) solution method is employed with which a transported PDF equation is solved in combination with Flamelet Generated Manifold (FGM) for high accuracy and computational efficiency. In all cases, the pilot fuel ignites before interacting with the H2 jet and thus reaction rate and chemical composition are computed as the weighted average of the corresponding values taken for two separated FGM tables generated for the two fuels. Pressure measurements and high-speed schlieren imaging performed in a preburn-type optical constant volume combustion chamber (CVCC) with n-heptane (nC7H16) pilot fuel were used to validate the EMCF+FGM model. The application focus is how H2 ignition and combustion is affected when the nC7H16 is injected prior to or after the main H2 jet. EMCF+FGM computed heat release rate and flame structure were compared with experimental data and results from conventional FGM model based on presumed PDF. When applied to H2DDI combustion, the EMCF+FGM model successfully reproduces flame structures and heat release rate under different injection strategies, including the transition towards partially-premixed combustion when the nC7H16 pilot follows the main H2 injection. Moreover, analysis of heat release rate from different stochastic fields can provide a useful indication about cyclic variability and combustion stability.