Cyclic Variation Research Articles

Mitigation of Urban Heat Island Effects by Thermochromic Asphalt Pavement

Asphalt road pavements are usually dark and, consequently, have a low albedo. Therefore, they absorb energy as heat, increasing the Urban Heat Island (UHI) effect, which impacts the environment, energy consumption, and human health. Through the functionalization with thermochromic materials (TM), this work aims to develop a smart asphalt pavement able to change its surface color, increasing the reflectance, and thus mitigate this phenomenon. To achieve this goal, asphalt substrates were functionalized by a surface spray coating of a thermochromic solution (TS) containing aqueous solution of thermochromic microcapsules (thermocapsules), dye, and epoxy resin. To evaluate the functionalization features, Fourier Transform Infrared Spectroscopy (FTIR), and Thermal Differential test (TDT) with cyclic temperature variation were performed in the functionalized asphalt binder. Moreover, Scanning Electron Microscopy (SEM), Energy-Dispersive X-ray Spectrometry (EDS), a Quick Ultraviolet Accelerated Weathering Test (QUV) with Colorimetry test, and an adaptation of the Accelerated Polishing Test (APT) were performed on the functionalized asphalt mixture. The results indicate that the functionalization of asphalt substrates with TS exhibits a reversible color-change ability, higher luminosity values when subjected to temperatures above 30 °C, and wear resistance.

Quantum cosmology in coupled Brans–Dicke gravity: A Noether symmetry analysis

This work deals with a multi-field cosmological model in a spatially flat FLRW spacetime geometry. The usual Brans–Dicke (BD) field and another scalar field are minimally coupled to gravity while they interact with each other through the Kinetic terms. The main aim of this work is to examine whether the model is compatible with cosmic observations. So cosmological solutions are obtained using symmetry analysis only. By imposing Noether Symmetry to the Lagrangian of the system, the potential of the scalar field as well as the coupling function had been determined. The classical solutions are determined after simplifying the Lagrangian using cyclic variables. Finally, Wheeler–DeWitt (WD) equation in quantum cosmology has been formulated and conserved momenta corresponding to Noether symmetry will show the periodic part of the wave function and it helps to have the complete integral for the wave function.

Effect of Premenstrual Stress on Reaction Time among Medical and Dental Students of a Medical College in Kathmandu, Nepal

The cyclical variation of ovarian hormones during the menstrual cycle has been implicated as the causative factor for many psychological and physical symptoms referred as premenstrual syndrome (PMS) causing varying degree of stress in females. This study is aimed to find out whether premenstrual stress might cause any alteration in the visual reaction time (VRT) in pre-menstrual and post-menstrual phase. Reaction time is an efficient non-invasive tool to evaluate the sensorimotor efficacy of a person. A cross sectional observational study was carried out in consenting and regularly menstruating 86 undergraduate medical and dental students of age ranging from 18-22 years, for a study period of April 2022 to June 2022. PMS was screened by using the PSST (premenstrual symptoms screening tool) to evaluate the incidence of PMS and the degree of premenstrual stress among the participants. All the participants showed some degree of PMS with 53.4% showing mild and 46.5% showing moderate to severe symptoms while none showed premenstrual dysphoric disorder (PMDD). A significant difference in body weight and visual reaction time (P<0.0001) was observed between the premenstrual phase and postmenstrual phase (54.6 ± 7.23 kg Vs 54.2 ± 7.24 kg and 0.959 ± 0.271ms vs 0.811 ± 0.138ms, respectively) irrespective of the PMS degree. The results indicate that premenstrual stress do affect the sensorimotor efficacy in females having PMS.

Investigating the Origins of Cyclic Variability in Internal Combustion Engines Using Wall-Resolved Large Eddy Simulations

Abstract Modern internal combustion engines (ICE) operate at the ragged edge of stable operation characterized by high cycle-to-cycle variations (CCV). A key scientific challenge for ICE is the understanding, modeling, and control of CCV in engine performance, which can contribute to partial burns, misfire, and knock. The objective of this study is to use high-fidelity numerical simulations to improve the understanding of the causes of CCV. Nek5000, a leading high-order spectral element, open source code, is used to simulate the turbulent flow in the engine combustion chamber. Multicycle, wall-resolved large-eddy simulations (LESs) are performed for the General Motors (GM), Transparent Combustion Chamber (TCC-III) optical engine under motored operating conditions. The mean and root-mean-square (rms) of the in-cylinder flow fields at various piston positions are validated using particle image velocimetry (PIV) measurements during the intake and compression strokes. The large-scale flow structures, including the swirl and tumble flow patterns, are analyzed in detail and the causes for cyclic variabilities in these flow features are explained. The energy distribution across the different scales of the flow are quantified using one-dimensional (1D) energy spectra, and the effect of the tumble breakdown process on the energy distribution is examined. The insights from this study can help us develop improved engine designs with reduced cyclic variabilities in the in-cylinder flow leading to enhanced engine performance.

Posidonia bonsai: Dwarf Posidonia oceanica shoots associated to hydrothemal vent systems (Panarea Island, Italy)

Very small-sized shoots of the Mediterranean seagrass Posidonia oceanica, defined as “bonsai” shoots, were found in areas with most intense CO2 emissions and low pH associated with four vents systems off Panarea island (Aeolian Archipelago, Sicily, Southern Tyrrhenian Sea). Bonsai shoots were sampled in September 2021 and October 2022: Bottaro crater (8 m depth), Camp 7 (16 m and 21 m), Black Point (20 m) and Hot/Cold Points (10 m). They had 2–6 leaves, and adult-intermediate leaves were 5–21 cm long and 3.5–7 mm wide, with leaf shoot surface ranging 4.8 and 44.5 cm2, and shoot leaf biomass between 16 and 89 mg (d.w.). These values were all significantly lower (t-test p < 0.006–0.0001) than those measured in normal-sized shoots collected within the vents and in control sites not affected by gas emissions. Bonsai shoots had 86–89% lower leaf surface, and 61–75% lower leaf biomass than all normal-sized shoots measured. The sheath thickness of the bonsai shoots was very low (0.1–0.8 mm), and the temporal trend of sheath thickness along the rhizome (lepidochronology) showed an irregular pattern, without the clear cyclical seasonal variation typical of normal-sized shoots. The reasons of size reduction and lack of temporal cycle in lepidochronology are discussed in the light of plant acclimatization and the constraints imposed by the continuous exposure to the stressful conditions of seawater acidification and presence of phytotoxic gases (e.g. hydrogen sulfide) in the vents.

Analysis of Thermo-Hygrometric Conditions of an Innovative Underwater Greenhouse

Nemo’s Garden® Project aims at creating a green, alternative, and original agriculture system based on underwater greenhouses (biospheres) developed for areas where plant growth is difficult in the terrestrial environment due to climate conditions and new global warming issues. Experiments were designed and performed to measure the thermal and hygrometric behaviour inside the biosphere; a simple theoretical model was developed to analyse the temperature and humidity of the air inside the biosphere in dynamic conditions and to interpret the experimental observations. The main findings of this research were: (i) the photosynthetically active radiation measured inside the underwater biosphere was 25–30% of that at sea level, (ii) the air temperature and relative humidity inside the biosphere showed cyclic daily variations that permitted a water evaporation/vapour condensation process, allowing the self-production of water for plant irrigation, and (iii) the results given by the lumped-parameter theoretical model were in a good agreement with the experiments.

Climate-controlled organic matter accumulation as recorded in the Upper Jurassic Argiles de Châtillon Formation, a shallow-marine counterpart of the Kimmeridge Clay Formation

AbstractMudstones from the Argiles de Châtillon Formation exposed in the Boulonnais region of Northern France represent a proximal lateral equivalent of the organic-rich Kimmeridge Clay Formation. The Argiles de Châtillon Formation is composed of two subunits that straddle the Kimmeridgian–Tithonian boundary. Each subunit contains an organic-rich interval. The two conspicuous organic-rich intervals have been linked to either periods of high sea level or greenhouse warming. Here, we use palynology to further understand climate and environmental mechanisms that drove organic matter enrichment. We use bulk organic carbon isotope records (δ13Corg) to correlate the Boulonnais sections with those of the Kimmeridge Clay Formation. The palynological results suggest that the stratigraphically lower organic-rich interval (Kimmeridgian) was deposited under suboxic to anoxic stratified conditions. A large-scale climate shift from cooler/humid to warmer/arid conditions marked the Kimmeridgian–Tithonian boundary, influencing organic matter enrichment in the stratigraphically higher organic-rich interval (Tithonian). In contrast with the lower organic-rich interval, there are no indications of stratified conditions for the higher organic-rich interval. Within this thicker organic-rich interval, cyclic variations in amorphous organic matter distribution, total organic carbon and δ13Corgtrends on a 2 m scale are observed. They co-occur with fluctuations of the palynological assemblages, indicative of more humid versus arid climate conditions, likely alternating on a ∼100 kyr eccentricity timescale. Our results show that under the most humid phases of these overall arid climate conditions, sulfurization of carbohydrates was the dominant control on organic matter preservation. This climate-controlled process that drives organic matter enrichment in the Tithonian can be recognized on a basin-wide scale.

Quantification and characterization of the microstructural damage of recycled aggregate self-compacting concrete under cyclic temperature changes

Recycled Aggregate (RA) usually increases porosity and weakens Interfacial Transition Zones (ITZs) of concrete, which favors the appearance of internal thermal damage. Four Self-Compacting Concrete (SCC) mixes with coarse and fine RA were subjected to positive and negative cyclic temperature variations to characterize their thermal damage and quantify its effects. Two damage mechanisms were found. On the one hand, micro-cracks appeared in the ITZs. On the other hand, micro-cracks arose from the micro-pores and propagated through the cementitious matrix. Both damage mechanisms were promoted by the use of coarse and fine RA, respectively. The damage was most notable at sub-zero temperatures and when adding coarse RA. Furthermore, it primarily affected compressive strength, although ultrasonic pulse velocity and hardened density also decreased, which served as non-destructive indicators to indirectly quantify the level of thermal internal damage of SCC.

Effect of coil charge duration on combustion variability and flame morphology in a GDI engine working in lean burn conditions

Spark ignition (SI) and subsequent flame front development exert a significant influence on cyclic variability of internal combustion engines (ICEs). The increasing exploitation of lean air-fuel mixtures in SI engines to lower fuel consumption and CO2 emissions is driving the scientific community towards the search for innovative combustion strategies. Moreover, although lean combustion has been widely investigated and an important number of studies is already present in literature, the high cyclic variability typical of this combustion process still represents a major hinder to its exploitation. This study aims to investigate the effects of increasing ignition energy on combustion characteristics of lean mixtures. Tests were performed on an optically accessible gasoline direct injection (GDI) engine that allowed to investigate the correlation between the thermodynamic results and spark arc-flame morphology. Engine speed was fixed at 2000 rpm, a relative air fuel ratio (AFRrel) of about 1.3 was selected and ignition timing was set at 12 crank angle degrees (CAD) bTDC. Coil charge duration was swept from 10 to 40 CAD. Two intake pressure levels were investigated, the first corresponding to wide open throttle under naturally aspirated operating mode, the second with an intake pressure of 1.2 bar, thus corresponding to a boosted operating condition. Two dedicated scripts built using NI Vision were employed for image processing, allowing the evaluation of temporal and spatial evolution of the early stages of combustion. Arc elongation and flame front contour were used as correlation parameters that characterize flame kernel inception and development. The results confirm that, as expected, the increase of the coil charge duration tends to reduce cyclic variability in terms of engine output. The optical investigations revealed that for both examined cases the standard deviation related to the wrinkling effect on flame edge at CA5 decreased as the coil charge duration increased.

Cyclic Variability in Brightness of the Young Solar Analog BE Ceti

Cyclic Variability in Brightness of the Young Solar Analog BE Ceti

Cyclic Variations of Active Regions Violating the Hale’s Polarity Law in 1989–2020 and in the Synthetic Cycle

Cyclic Variations of Active Regions Violating the Hale’s Polarity Law in 1989–2020 and in the Synthetic Cycle

Computational investigation of the transient cyclic thermal distortion of funnel shaped mould in thin slab continuous casting process

The response of the thin slab continuous casting mould subjected to thermal and mechanical interactions needs to be studied, since they alter the shape of the mould. A 3D thermomechanical model is developed using non-linear kinematic and isotropic plasticity models along with the creep model to calculate the transient cyclic distortion, residual stress, and elastic–plastic-creep strains in an assembly of funnel-shaped copper mould and waterbox, as the mould undergoes multiple heating cycles in its lifetime. Most of the funnel transition region of the wide face is accumulated with higher temperatures and hence, displacements and strain distributions are maximum in that region. Distortion of the narrow face is majorly affected by the mechanical boundary condition. It is observed that excluding the time dependent creep model highly overestimated the mechanical behaviour of the mould. It is also observed that there is a cyclic variation of distortion of the mould towards the liquid metal side during the casting process and away from the liquid metal side during the cooling process which causes the development of residual stresses inside the mould. This phenomenon further leads to reduction in the magnitude of distortion during subsequent heating cycles of casting operation.

Cyclic Variations of the Polarity of the Photospheric Magnetic Field

Cyclic Variations of the Polarity of the Photospheric Magnetic Field

Response of perforated H-pile subjected to coupled lateral displacement history and axial loading

ABSTRACT The substructure of an integral abutment bridge is designed to accommodate the lateral demand induced by the expansion and contraction of the bridge deck. The assembly of H-piles oriented about their weak axis of bending and aligned in a single row with a rigid connection to the abutment is most preferred for supporting the integral abutment bridges. The weak axis orientation of H-pile allows for higher displacement capacity, thus accommodating the cyclic thermal demand induced by a superstructure. The hysteretic response of H-piles is suggestive of the early onset of the plastic hinge formation, which helps in accommodating the cyclic demand. The H-piles in the integral abutment bridge experience low cycle fatigue induced by cyclic thermal variations, resulting in the buckling of flanges at the critical zone. This study assesses the impact of perforation made on H-pile flanges at the critical buckling zone. In this study, six unique geometries of perforations are modelled and analysed using combined nonlinear kinematic and isotropic hardening formulation. The hysteretic response of the perforated H-pile models has been compared with an unperforated model to assess the proposed perforation geometry's impact on the H-pile's hysteretic response.

Magnetic fluxes of solar active regions of different magneto-morphological classes – I. Cyclic variations

ABSTRACT Data for 3046 solar active regions (ARs) observed since 1996 May 12 to 2021 December 27 were utilized to explore how the magnetic fluxes from ARs of different complexity follow the solar cycle. Magnetograms from the Michelson Doppler Imager instrument on the Solar and Heliospheric Observatory and from the Helioseismic and Magnetic Imager instrument on the Solar Dynamics Observatory were utilized. Each AR was classified as a regular bipolar AR (classes A1 or A2), or as an irregular bipolar AR (class B1), or as a multipolar AR (classes B2 or B3). Unipolar ARs were segregated into a specific class U. We found the following results. Unsigned magnetic fluxes from ARs of different classes evolve synchronously following the cycle, the correlation coefficient between the flux curves varies in a range of 0.70–0.99. The deepest solar minimum is observed simultaneously for all classes. Only the most simple ARs were observed during a deepest minimum: A1- and B1-class ARs. The overall shape of a cycle is governed by the regular ARs, whereas the fine structure of a solar maximum is determined by the most complex irregular ARs. Approximately equal amount of flux (45–50 per cent of the total flux) is contributed by the A-class and B-class ARs during a solar maximum. Thus, observations allow us to conclude that the appearance of ARs with the magnetic flux above 1021 Mx is caused by the solar dynamo that operates as a unique process displaying the properties of a non-linear dynamical dissipative system with a cyclic behaviour and unavoidable fluctuations.

Cyclic variability of eastern Bering Sea jellyfish relates to regional physical conditions

Globally, there have been few long-term (>30 years), shelf-wide surveys of jellyfish that have allowed for the examination of how populations might respond to changing climatic and oceanographic conditions. One region where investigation of jellyfish responses to climate variability is possible is the eastern Bering Sea, where jellyfish biomass, primarily that of Chrysaora melanaster, has fluctuated dramatically since 1982, when systematic collections of these medusae began. Our previous investigations of a 27-year time series indicated that the timing of the jellyfish biomass increases and declines coincided with transitions between climatic regimes. In the current study, we used updated jellyfish catch and environmental data from 1982 to 2017 and reran our generalized additive model (GAM) analyses to determine if models using solely physical variables and lag of jellyfish biomass could describe accurately the increases and subsequent decreases observed in this jellyfish biomass index. GAMs hindcasting jellyfish biomass for the period 1982–2017 explained a large fraction of the variance, 92.3 % and 86.4 %, for the southeast (SE) and northwest (NW) portions of the survey area, respectively, using jellyfish biomass in the preceding year and physical variables (SE: ice retreat, sea-surface temperature, wind mixing, wind stress and current displacement; NW: sea-surface temperature, ice cover, wind stress and current displacement). We developed more parsimonious models by calculating the variance inflation factor for each term and dropping highly correlated terms from the models. The resulting GAMs continued to explain a significant portion of the variance in jellyfish biomass, i.e., 78.2 % and 73.5 %, in the southeast and northwest survey areas, respectively. Jellyfish biomass in the SE region was correlated with the jellyfish biomass in the preceding year and with wind mixing, wind stress and current displacement. In the NW region, jellyfish biomass was correlated with biomass from the preceding year, and with summer sea-surface temperature and current displacement. Jellyfish biomass in the eastern Bering Sea did not increase during warm periods, as has been speculated to occur elsewhere. Jellyfish, which are both predators and competitors of fish, appear to be responding to changes in physical conditions and are important indicators of ecosystem change in the eastern Bering Sea. The development of models that use physical parameters, as opposed to biological variables that are often not readily available, is key to predicting jellyfish abundance and their impacts on commercially important species.

Influence of Intake Port Structure on the Performance of a Spark-Ignited Natural Gas Engine

Spark-ignited natural gas engines have received increasing attention in the heavy-duty market due to their low cost and reliability advantages. However, there are still some issues with natural gas engines retrofitted from 10 to 15 L diesel engines, which is a valuable medium-term goal for the automotive industry. In this work, the effect of intake port structure on the performance of a spark-ignited heavy-duty natural gas engine was investigated by multidimensional numerical simulations. A newly designed intake port was proposed, with strengthened in-cylinder turbulent kinetic energy and homogeneous air-fuel mixtures. Bench tests show that the proposed intake port has impressive thermal efficiency, cycle variation, and acceptable emissions performance. The effective thermal efficiency improves from 41.0% to 41.4%, and the cycle variation is 36% lower than traditional schemes. However, with the accelerated flame propagation, the in-cylinder temperature and NOx emission of the mixed-flow port increase while the CO emission decreases. In summary, a proper balance of in-cylinder swirl and tumble flow can significantly affect the economy and stability of natural gas engines. The proposed structure solves the inherent problems of slow natural gas flame propagation and harmful cyclic variations.

Desynchronizing the sleep---wake cycle from circadian timing to assess their separate contributions to physiology and behaviour and to estimate intrinsic circadian period.

Circadian clocks drive cyclic variations in many aspects of physiology, but some daily variations are evoked by periodic changes in the environment or sleep-wake state and associated behaviors, such as changes in posture, light levels, fasting or eating, rest or activity and social interactions; thus, it is often important to quantify the relative contributions of these factors. Yet, circadian rhythms and these evoked effects cannot be separated under typical 24-h day conditions, because circadian phase and the length of time awake or asleep co-vary. Nathaniel Kleitman's forced desynchrony (FD) protocol was designed to assess endogenous circadian rhythmicity and to separate circadian from evoked components of daily rhythms in multiple parameters. Under FD protocol conditions, light intensity is kept low to minimize its impact on the circadian pacemaker, and participants have sleep-wake state and associated behaviors scheduled to an imposed non-24-h cycle. The period of this imposed cycle, Τ, is chosen so that the circadian pacemaker cannot entrain to it and therefore continues to oscillate at its intrinsic period (τ, ~24.15 h), ensuring circadian components are separated from evoked components of daily rhythms. Here we provide detailed instructions and troubleshooting techniques on how to design, implement and analyze the data from an FD protocol. We provide two procedures: one with general guidance for designing an FD study and another with more precise instructions for replicating one of our previous FD studies. We discuss estimating circadian parameters and quantifying the separate contributions of circadian rhythmicity and the sleep-wake cycle, including statistical analysis procedures and an R package for conducting the non-orthogonal spectral analysis method that enables an accurate estimation of period, amplitude and phase.

Combustion and emissions characteristics of methanol/gasoline CISI engines under different injection modes

Methanol was a promising alternative fuel for spark ignition engines due to its liquid nature, large octane number and high oxygen content. The combined injection technology had the advantages of greater control flexibility, less engine knock tendency, and less engine-out emissions. However, the preferable injection mode of methanol/gasoline dual fuel engine was rarely reported. In this study, the combustion and emission characteristics of methanol/gasoline dual fuel engine with different injection modes, methanol direct injection plus gasoline port injection (MDI + GPI) or gasoline direct injection plus methanol port injection (GDI + MPI), were studied experimentally. The results showed that MDI + GPI mode was preferred for methanol/gasoline dual fuel engines, as this mode yielded higher engine brake effective mean pressure, larger heat release rate, lower cyclic variation, and less particle number emissions. An unimodal nucleation pattern particle size distribution can be observed for the MDI + GPI mode, which was beneficial for the after-treatment of particles in gasoline particle filter.

Orbitally forced chemical weathering in the Late Cretaceous northeastern China: Implications for paleoclimate change

The International Continental Scientific Drilling Project of Cretaceous Songliao Basin has recovered a complete Cretaceous terrestrial sedimentary record in northeastern China, providing a unique opportunity to understand the terrestrial climate change during the Cretaceous period. In this study, we present high-resolution geochemical records from Members 3 and 4 of the Quantou Formation in the SK-1 South borehole. The findings show that samples from Members 3 and 4 of the Quantou Formation originated from a source area of a homogeneous composition. Most of the samples were sediments that underwent the first round of weathering. The geochemical proxies (Th, CIA, CIW, τ Na ) and average value of the CIA proxy indicate that the strata have been subjected to moderate chemical weathering. The weathering intensity trend was divided into four evolutionary stages based on the CIA proxy: the steady lower part (1915–1878 m), the slowly rising lower and middle part (1878–1815 m), the middle and upper part (1815–1800 m) showing the highest values, and the gently fluctuating upper part (1800–1783 m). Precession, obliquity, and short-eccentricity signals were recognized in the proxies of Th, τ Na , corrected CIA, and corrected CIW from Members 3 and 4 of the Quantou Formation, including about seven short-eccentricity cycle periods with a duration of ∼700 ka. The high peaks in short-eccentricity correspond to the high values of Th, corrected CIA, and corrected CIW proxies, and are consistent with the amplitudes of precession signals preserved in τ Na during humid periods. During strong precession, the enhanced seasonal contrasts increased humidity, which intensified chemical weathering. The paleoclimatic pattern of interaction between the monsoon-like system and westerlies in the Cretaceous Songliao Basin may be the underlying interpretation that causes cyclic variation in the chemical weathering proxies in Members 3 and 4 of the Quantou Formation. • Reconstruction of historical chemical weathering using multiple weathering proxies. • Humid climate derived from a non-linear response of the climate system to precession. • Interaction between the monsoon-like system and westerlies may be the interpretation causing cyclic variation.