Main Oscillation Research Articles

Study of transient behaviors of wavefront error caused by natural convection for improving mirror seeing.

Astronomical seeing parameters calculated based on the Kolmogorov turbulence model cannot fully evaluate the effect of the natural convection (NC) above a solar telescope mirror on the image quality, as the convective air motions and temperature variations of the NC are significantly different from the Kolmogorov turbulence. In this work, a new method based on the transient behaviors and frequency characteristics of NC-related wavefront error (WFE) are investigated in detail and used to evaluate the image quality degradation caused by a heated telescope mirror, aiming to make up for the deficiency of astronomical seeing parameters with the conventional method in evaluating the image quality degradation. Transient computational fluid dynamics (CFD) simulations and WFE calculations based on discrete sampling and ray segmentation are performed to quantitatively evaluate the transient behaviors of the NC-related WFE. It clearly exhibits apparent oscillatory characteristics, which are coupled by main oscillation with low frequencies and minor oscillation with high frequencies. Moreover, the generation mechanisms of two types of oscillations are studied. The conspicuous oscillation frequencies of the main oscillation caused by heated telescope mirrors with varying dimensions are primarily lower than 1 Hz, suggesting that active optics may be adopted to correct the main oscillation of NC-related WFE while the adaptive optics may correct the minor oscillation. Furthermore, a mathematical relationship between WFE, temperature rise, and mirror diameter is derived, revealing a significant correlation between WFE and mirror diameter. Our work suggests the transient NC-related WFE should be considered as one of the critical supplements to the mirror seeing evaluation.

Model for Combustion Instability in Hybrid Rocket Engines Burning Liquefying Fuels

Starting from the data measured in several static firings of two laboratory-scale hybrid rocket engines of different sizes burning gaseous oxygen with either a liquefying fuel or a pyrolyzing polymer, a mechanism for the combustion instability observed only with liquefying fuel is suggested. With the latter type of fuels, regression rate is increased for the formation of an unstable liquid layer on the grain surface, for which liquid fuel structures are entrained into the gas stream and burn, upon vaporization and mixing, far from the surface. Based on this circumstance, the hypothesis of a time delay to burn, with the resulting effect of triggering longitudinal acoustic modes of the system, is formulated. A simplified analytical acoustic model of a series of interconnected ducts with different cross sections and gas properties is preliminarily addressed, which allowed demonstrating the acoustic nature of the main pressure oscillation peaks measured in three firing tests along with the influence of the oxygen-feeding line on the system acoustics. Finally, by leveraging an existing acoustic model of the hybrid rocket combustion chamber including the effects of cross-sectional discontinuities and distributed fuel mass addition and combustion, the linear stability of the system is analyzed, whose results are apt to reproduce the experimental findings.

Electronic Structure and Hole Transfer of All B-DNA Dimers and Homopolymers, via the Fishbone-Wire Model.

We employ the Tight Binding Fishbone-Wire Model to study the electronic structure and coherent transfer of a hole (the absence of an electron created by oxidation) in all possible ideal B-DNA dimers as well as in homopolymers (one base pair repeated along the whole sequence with purine on purine). The sites considered are the base pairs and the deoxyriboses, with no backbone disorder. For the time-independent problem, we calculate the eigenspectra and the density of states. For the time-dependent problem after oxidation (i.e., the creation of a hole either at a base pair or at a deoxyribose), we calculate the mean-over-time probabilities to find the hole at each site and establish the frequency content of coherent carrier transfer by computing the Weighted Mean Frequency at each site and the Total Weighted Mean Frequency of a dimer or polymer. We also evaluate the main oscillation frequencies of the dipole moment along the macromolecule axis and the relevant amplitudes. Finally, we focus on the mean transfer rates from an initial site to all others. We study the dependence of these quantities on the number of monomers that are used to construct the polymer. Since the value of the interaction integral between base pairs and deoxyriboses is not well-established, we treat it as a variable and examine its influence on the calculated quantities.

Mathematical Model of a Main Rhythm in Limbic Seizures

While synchronization in the brain neural networks has been studied, the emergency of the main oscillation frequency and its evolution at different normal and pathological states remains poorly investigated. We propose a new concept of the formation of a main frequency in limbic epilepsy. The idea is that the main frequency is not a result of the activity of a single cell, but is formed due to collective dynamics in a ring of model neurons connected with delay. The individual cells are in an excitable mode providing no self-oscillations without coupling. We considered the ring of a different number of Hodgkin–Huxley neurons connected with synapses with time delay. We have shown that the proposed circuit can generate oscillatory activity with frequencies close to those experimentally observed. The frequency can be varied by changing the number of model neurons, time delay in synapses and coupling strength. The linear dependence of the oscillation period on both coupling delay and the number of neurons in the ring was hypothesized and checked by means of fitting the values obtained from the numerical experiments to the empirical formula for a constant value of coupling coefficient.

ЗБУДЖЕННЯ ХВИЛІ TЕ01 У КРУГЛОМУ ХВИЛЕВОДІ ЗА ДОПОМОГОЮ ВИЩИХ ТИПІВ КОЛИВАНЬ ВІДКРИТОГО РЕЗОНАТОРА

Subject and Purpose. Peculiarities of the TE01 wave excitation in a circular waveguide located in the center of the flat mirror of a hemispherical open resonator (OR) are studied using the OR oscillation type TEM30q and the OR degenerate oscillation type TEM in the extremely high frequency (EHF) range. Methods and Methodology. The efficiency of the circular-waveguide TE01 wave excitation using the TEM30q and TEM11q types of OR oscillations is evaluated through the factor of antenna surface utilization. Amplitude distributions of the OR oscillation fields were measured by the trial body method. Results. It has been established that the efficiency, h, of the TE01 wave excitation in the circular waveguide is not high when it is by use of the OR oscillation ТЕМ30q. Things are different when the TE01 wave is excited with the inner ring of the TEM11q degenerate oscillation field whereby the h value shoots up to 95.5%, the circular waveguide section radius being a = 0.993w0, where w0 is the radius of the field spot of the main oscillation type TEM00q on the OR flat mirror. The experimental studies have confirmed that the TE01 wave excitation in the waveguide has high efficiency. The attachment of the circular oversized waveguide section worsens the OR loss by no more than 0.9 dB. The presence of the circular waveguide makes the TEM3012 oscillation type transform into the TEM1112 degenerate oscillation. Conclusions. The considered OR can be used as a storage resonator in the construction of electromagnetic pulse compressors in the EHF range, since the resonant system loss increases insignificantly, and the circular waveguide itself is oversized. It is easy to implement an interference switch in such a waveguide.

Analysis of the variation tendency and influencing factors of reference evapotranspiration in Shandong Province, China

AbstractReference evapotranspiration (ET0) is an important part of the water and energy cycles during crop growth. The study of its changing trend is of significance for guiding efficient water utilization and reasonable regulation of agricultural production. Based on daily meteorological data, including temperature, relative humidity, wind speed and sunshine hours, from 38 surface meteorological stations in Shandong Province from 1980 to 2019, the FAO56 Penman–Monteith formula was used to calculate the ET0 and analyse trend and influencing factors, combined with the methods of climate tendency rate, Morlet wavelet, sensitivity analysis and contribution rate analysis. ET0 had 26–30 main oscillation cycles during the 1980–2019 period, and 28‐, 18‐ and 8‐year time scales corresponded to the first, second and third main cycles of ET0, respectively, which determined the characteristics of ET0 change in the past 40 years. The annual average ET0 was significantly positively correlated with average temperature (T), wind speed (WS) and sunshine daily hours (SSD) and significantly negatively correlated with average relative humidity (RH), among which WS, SSD and RH were the main factors affecting ET0. On this basis, because T was not the dominant factor affecting ET0 change, a simplified ET0 calculation algorithm based on seasonal temperature was established that had high goodness of fit R2 accuracy. This study quantitatively analysed the periodic changes and causes of ET0 from a spatio‐temporal view and provided a scientific basis for the rational regulation of agricultural production in Shandong Province.

Spectral Broadening Suppressed by a Gain-Enhanced Fiber in Polarization Maintaining High-Power Systems

A gain-enhanced 10/125 μm polarization-maintaining Yb-doped fiber (PMYDF), with the cladding absorption of 7.5 dB/m at 976 nm, for narrow linewidth linearly polarized fiber oscillator or amplifiers is presented. By utilizing the gain-enhanced PMYDF in an all-fiber laser oscillator, an output power of 123 W is achieved with applying appropriate bending strategies and thermal management, corresponding to the slope efficiency of 86.7%. By applying the gain-enhanced PMYDF in seed, an increase of 34% in the longitudinal mode interval is effectively achieved compared to the commercial PMYDF, while the number of longitudinal modes is only 75%. According to the main oscillation power amplification (MOPA) system, the total amount of spectral broadening applying the seed with the gain-enhanced PMYDF are only 67%, 64% and 54% of applying the seed with the commercial PMYDF, corresponding to co-pumping, bi-pumping and counter-pumping schemes, respectively.

Исследование возможности моделирования вибраций корпуса насоса из-за воздействия нестационарных гидродинамических сил

Increase in the service life and noise reduction in pumps is an important area in modern pump engineering. An attempt was made to introduce conjugate calculations in verifying correct operation of the mathematical model as the first step and identifying the main oscillation frequencies of the pump housing subsequently. The FSI interface was used in conjugate calculations at the boundary between liquid and solid media. The obtained oscillation signals were analyzed using the Fourier analysis to identify the main parasitic frequencies in the pump. It was expected that the main parasitic frequency would be the blade frequency. As a result of calculations, it became possible to verify correct operation of the mathematical model by applying it to the simplest model of a glass, which behavior could be easily explained. The mathematical model was tested on cantilever and multistage pumps, demonstrated good results and made it possible to establish that blade frequency was the main oscillation frequency.

Multi-decadal oscillations of surface temperatures and the impact on temperature increases

The last IPCC assessment report indicated that natural climate variability could temporarily amplify or obscure anthropogenic climate change on decadal time scales. Here we analyse global mean surface temperatures in terms of such long-period variations. We find two main oscillations, a strong oscillation with a period of about 70 years and an amplitude of about 0.09 K and a quasi-bidecadal oscillation with an amplitude of about 0.06 K. The strong oscillation shows large hemispheric differences. In the Northern hemisphere the period is longer and the amplitude is larger (about 82 years and 0.18 K) compared to the Southern hemisphere (about 47 years and 0.065 K). No obvious hemispheric differences are observed for the quasi-bidecadal oscillation. Such long-period oscillations can strengthen or weaken the temperature increase if the oscillation positively or negatively adds to the underlying long-term trend.

Long term oscillations of Mediterranean sardine and anchovy explained by the combined effect of multiple regional and global climatic indices

It is widely known that the abundance and distribution dynamics of populations of small pelagic clupeid fish, such as sardines and anchovies, are affected by large-scale climate variability, which may lead to changeovers to new regimes of small pelagics. However, long-distance climatic oscillations, such as El Niño/La Niña and the Pacific Decadal Oscillation, have been little explored in the Western Mediterranean Sea. We investigated the possible effects of the South Oscillation Index (i.e. the atmospheric oscillation coupled with the El Niño/La Niña) and Pacific Decadal Oscillation on fluctuations in catches of European anchovy (Engraulis encrasicolus) and sardine (Sardina pilchardus) in the Western Mediterranean Sea, and their association with regional climate oscillations (i.e. the Atlantic Multidecadal Oscillation, the North Atlantic Oscillation, the Western Mediterranean Oscillation index, and the Arctic Oscillation). The study covered two periods: (a) landings between 1950 and 2016; and (b) abundance, biomass, and physical condition (i.e., relative condition index) between 2004 and 2016. The main large-scale climatic oscillations in the region were studied using General Additive Models to investigate the relationship between a time series of species measures of European sardine and anchovy from Geographical Subarea 06. Results show that the long-term Pacific Decadal Oscillation favours sardine landings, whereas the combined effect of the Western Mediterranean Oscillation Index and the Atlantic Multidecadal Oscillation favours anchovy. We discuss potential links between the present findings and changes in the plankton community caused by prevailing winds in the region driven by long-distance climate oscillations and their impact on the reduction in small pelagic fish populations in the study area.

Evidence of the climate control of strong seismicity in the Italian Apennines through groundwater recharge

This work explores the possibility that the destructive earthquakes occurring along the Apennine Chain in Italy are systematically triggered by groundwater recharge. The focus is on multi-year transitions toward phases of wet climate rather than on short-term heavy rainfall occurring in a few days or seasonally. The analysis takes into consideration the earthquakes with a moment magnitude of Mw ≥5.8 that have occurred since 1901. Their time distribution is compared with the fluctuations of the self-calibrated Palmer Drought Severity Index (scPDSI), an indicator of soil moisture, here assumed to be a proxy for groundwater recharge. It is found that the scPDSI evolved through six main oscillations lasting from 11 to 25 years, and that, with one exception, the strongest earthquake in each phase is placed within 2 years from the maximum of soil moisture. Based on a statistical test for pairs of point processes, such a coincidence indicates a significant synchrony between the two phenomena. In particular, the two strongest earthquakes of the study period (the 1915 Marsica earthquake and the 1980 Irpinia–Basilicata earthquake, with moment magnitudes of Mw 7.1 and 6.8, respectively) occurred exactly in the year of two of the largest peaks of scPDSI. The connection between wet climate conditions and the occurrence of strong earthquakes is further investigated by comparing the time distribution of Mw ≥6.1 historical earthquakes that have occurred since 1200 AD with the evolution of the Great Aletsch Glacier in Switzerland, representative of water accumulation at the continental level. Even in this case, the earthquakes clustered during time periods of increased precipitation and lower water evaporation, corresponding to the extreme phases of the Little Ice Age. The agreement of the results at different time scales and using different climate indexes leads to postulate a significant and systematic role of groundwater recharge in the triggering of large earthquakes along the Apennines. It is also suggested that the earthquakes might be triggered by pore-pressure propagation, where the necessary hydraulic continuity is made possible by the intersection of the shallow karst structures with the seismogenic faults.

Investigation of the mechanism of unsteady flow induced by cavitation at the tongue of a centrifugal pump based on the proper orthogonal decomposition method

To investigate the unsteady evolution characteristics and mechanism of cavitation at the tongue and its influence on the flow field in a centrifugal pump, numerical calculations were performed to research the occurrence and development of cavitation at the tongue under large flow rate (1.3Qd) conditions. The numerical calculation results were verified by experiments. The proper orthogonal decomposition (POD) method was used to decompose and reconstruct the flow field at the tongue of the centrifugal pump. The relationship between the typical frequency of pressure pulsation and the mainstream structure of the flow field was established. The POD method could accurately extract the coherent structure caused by cavitation and capture the unstable flow structure produced by vortex shedding. Under different available net positive suction head conditions, the first mode was the mainstream structural mode in the original flow field, with low-frequency and single-frequency components. The second, third, and fourth modes were the main oscillation modes of the original flow field and showed the characteristics of high frequency and multiple frequencies. High-order modes could capture the complex flow field structure caused by the change in the large-scale vortex structure induced by the unsteady pulsation of cavitation.

Effect of initial pressure on the propagation characteristics of supersonic turbulent jets in fuel jet ignition

The effects of initial pressure (Pini) on the propagation characteristics of supersonic turbulent jets (STJ) were studied experimentally in a constant volume chamber. Based on the top vortex motion, three types of flame propagation modes are identified: Mode 1, the vortex in the middle of the jet propagates; Mode 2, the vortex in the middle of the jet moves to the top and the tail; Mode 3, jet tail flame extinguished. Each mode follows a 3-stage propagation method: (a) a jet flame with a with a sharp drop in the flame tip velocity (VFTV); (b) a self-accelerating mushroom-shaped flame followed by turbulent flame with low frequency oscillation; (c) a turbulent flame with a drop in VFTV. The momentum dissipation causes the velocity to drop in stage I and stage III, and stage II is controlled by the eddy motion of the mushroom-shaped flame tip and the pulsation of the flow field. The experimental results show that higher Pini can stimulate a stronger interaction mechanism between flow field oscillation in the main combustion chamber (MCC) and chemical heat release oscillation in the pre-chamber (PCC). Based on an evaluation of the model correlations, we found that the jet penetration length showed a linear relationship with the product of the relative pressure fourth root and the time square root.

State-dependent modulation of thalamocortical oscillations by gamma light flicker with different frequencies, intensities, and duty cycles.

Rhythmic light flickers have emerged as useful tools to modulate cognition and rescue pathological oscillations related to neurological disorders by entrainment. However, a mechanistic understanding of the entrainment for different brain oscillatory states and light flicker parameters is lacking. To address this issue, we proposed a biophysical neural network model for thalamocortical oscillations (TCOs) and explored the stimulation effects depending on the thalamocortical oscillatory states and stimulation parameters (frequency, intensity, and duty cycle) using the proposed model and electrophysiology experiments. The proposed model generated alpha, beta, and gamma oscillatory states (with main oscillation frequences at 9, 25, and 35 Hz, respectively), which were successfully transmitted from the thalamus to the cortex. By applying light flicker stimulation, we found that the entrainment was state-dependent and it was more prone to induce entrainment if the flicker perturbation frequency was closer to the endogenous oscillatory frequency. In addition, endogenous oscillation would be accelerated, whereas low-frequency oscillatory power would be suppressed by gamma (30–50 Hz) flickers. Notably, the effects of intensity and duty cycle on entrainment were complex; a high intensity of light flicker did not mean high entrainment possibility, and duty cycles below 50% could induce entrainment easier than those above 50%. Further, we observed entrainment discontinuity during gamma flicker stimulations with different frequencies, attributable to the non-linear characteristics of the network oscillations. These results provide support for the experimental design and clinical applications of the modulation of TCOs by gamma (30–50 Hz) light flicker.

Change patterns of precipitation anomalies and possible teleconnections with large-scale climate oscillations over the Yangtze River Delta, China

Abstract In view of the key factor in regional hydrological processes and water resource management, the temporal patterns of precipitation anomalies and oscillations were detected by the Quantile Perturbation Method (QPM) and the Singular Spectrum Analysis (SSA) Method, and the spatial patterns were identified using the Principal Component Analysis (PCA) Method. In addition, the teleconnections and lagged influence with large-scale climate oscillations in the Yangtze River Delta (YRD) of China from 1957 to 2016 were also analyzed. Results showed that, temporally, the main oscillations of precipitation were all found to be 2, 7–11 and 3–4 years in the annual and seasonal scales. Precipitation quantiles are subject to strong temporal oscillations at (multi-)decadal time scales, with high and low anomalies at specific periods. Spatially, the whole region could be divided into two main sub-regions in annual and seasonal scales, respectively. Among the selected large-scale climate oscillations in this study, the Pacific Decadal Oscillation (PDO) has a stronger influence on precipitation in March, July and September, but significant correlations were detected in more than 18% of the total stations. These stations were mainly in the southeast regions. The North Pacific index (NP) controlled the precipitation in February (13.95% of the total stations) and October (37.21% of the total stations) in the north region. Generally, the indicators of the Southern Oscillation Index (SOI) and Oceanic Niño 4 SST Index (ONI) had the strongest influence in regional precipitation variations, but significant correlations were detected in more than 20% of the total stations in March, September, October and November. Also, large-scale climate oscillations have a delayed way on precipitation. Among the oscillations, the Arctic Oscillation (AO) and North Atlantic Oscillation (NAO) showed that significant cross-correlations on precipitation were 0 and 3–5 months, respectively. NP showed significant cross-correlations with precipitation in many stations when the lag time was 0–3 months. Generally, the PDO, SOI and ONI have a greater influence in the south region, mainly with the lag time of 0–3, 2–3 and 1–5 months, respectively. The results will provide a basis for taking relevant measures to deal with problems of meteorological disaster and water supplement under climate change.

Pattern of spatio-temporal variability of extreme precipitation and flood-waterlogging process in Hanjiang River basin

Based on the uniform distributed rainfall data in the Hanjiang River basin, the characteristics of spatio-temporal variability of extreme precipitation and flood-waterlogging process are diagnosed in terms of index definition and mathematical statistics. The study found that: (1) no significant trends of extreme rainfall for the entire basin were tested, but there was a jump variation in 1990s from abundance to dryness, accompanied by 20-year main periodic oscillation. Since 2000, the frequency of extremely heavy rain has increased significantly. (2) there is a spatial distribution pattern of lower in the northeast and higher in the southwest, and decreasing from upstream to downstream in the annual means of extreme precipitation. High-value centers are concentrated in the southwestern mountainous areas and the plains in the downstream, which are prone to form the distribution pattern of Central-North Radiation Type and Southeast-Northwest Type. (3) basin usually suffers 5–6 waterlogging processes per year, most of which were light or moderate grade, lasting 2–4 days. Since 2000, the flood-waterlogging process has shown evolution characteristics in increasing of the intensity, frequency, duration, and fluctuation, having strong continuity in the future. (4) affecting by climate and topography, spatial distribution of flood-waterlogging is uneven. Downstream and southwest of upstream are regularly the high-value centers, which are easy to form three kinds of distribution patterns, namely Northeast Radiation Type, Middle-lower Radiation Type and Middle-upper Radiation Type. Since the 21st century, the Hanzhong area and the watershed below Xiangyang both often encountered flood-waterlogging processes of high-intensity, long-duration, and high-frequency, which easy to induce flood disasters. Spatio-temporal variability of extreme precipitation and flood-waterlogging is a direct result of the rational development and utilization of water resources. We expect the results here to provide a deep insight into flood-waterlogging and serve as a reference for the watershed flood disaster response, rain-flood utilization, and optimal allocation of water resources.

Dynamic stability analysis of power grid in high proportion new energy access scenario based on deep learning

The “carbon peaking and carbon neutralization” scheme formulated to solve the power energy shortage makes the new energy units incorporated into the power grid on a large scale. The randomness and volatility caused by the high proportion of new energy access have a certain impact on the dynamic stability of the power grid. Based on the dynamic stability theory, this paper applies the dual-stream CNN algorithm in the deep learning technology to model, takes the power of each node and line as the input and the key eigenvalue as the output, quickly identifies the main oscillation modes of the power system, makes a qualitative evaluation. Combined with the actual power grid analysis, the interval oscillation frequencies of the system are 0.57 Hz and 0.53 Hz respectively, which belong to strongly damped oscillation and can be quickly subsided after being excited. It can be concluded that the dual-stream CNN algorithm can provide reliable technical support for subsequent dispatching operation, and is conducive to improving the safe and stable operation level of power system.

Temporal and Spatial Variation in O3 Concentration Near the Surface of Shandong Peninsula and Analysis of Potential Source Areas

The purpose of this study was to explore the temporal and spatial distribution characteristics and potential sources of ozone (O3) in the Shandong Peninsula over a long period of time based on the analysis of the temporal and spatial changes in O3 concentration in Shandong Peninsula from 2005 to 2020. We used wavelet analysis, the entropy weight method, and correlation analysis to discuss O3 and its influencing factors and researched the potential sources of O3 in Shandong Peninsula. The results showed that:① in terms of the time pattern, the near-surface O3 in Shandong Peninsula showed a "triple peak" trend from 2005 to 2020, reaching the maximum value of[(40.48±7.64) μg·m-3] in 2010 and a minimum value of[(36.63±5.61) μg·m-3] in 2013. The season was expressed as:summer[(42.49±1.7) μg·m-3]>spring[(40.65±0.6) μg·m-3]>autumn[(36.47±0.7) μg·m-3]>winter[(36.46±0.3) μg·m-3]. ② In terms of the spatial pattern, the O3 concentration of Shandong Peninsula gradually increased with the increase in latitude from 2005 to 2020, showing the characteristics of high concentrations in the east and west and low in the middle region. During the 16-year evolution of the O3 concentration, there was a 1.5 a main oscillation period. ③The analysis of meteorological conditions revealed that O3 concentration was positively correlated with temperature, precipitation, relative humidity, and sunshine hours, whereas pressure and wind speed were negatively correlated. In the analysis of social factors, soot (dust) emissions were the most obvious factor affecting the third indicator, with a weight of 0.25. ④ Through simulating the trajectory of airflow from different regions (Ji'nan and Qingdao), it was found that the ocean airflow contributed 10.69% to Jinan and 48.94% to Qingdao. There was 64.04% of the long-distance air mass transmission path coming from the northwest, and 43.69% of the short-distance air mass transmission path was from the Bohai Sea and the Yellow Sea, followed by Shandong Province with 21.01%. ⑤ The analysis of potential sources of O3 showed that the potential sources of Ji'nan were mainly distributed in Jinzhou, Liaoning Province, northern Jiangsu Province, Hubei Province, and Anhui Province, with a WPSCF value >0.6, and Qingdao's WPSCF value of >0.6 was mainly distributed in the Yellow Sea area. The O3 contribution of Jining City, Linyi City, Xuzhou City, Huaibei City, and Lianyungang City was >40 μg·m-3. The area with >45 μg·m-3 in Qingdao was mainly in the Yellow Sea. Through the analysis of potential sources in the Shandong Peninsula, particular attention should be paid to the supply of industrial sources in the surrounding areas and the marine sources provided by marine air pollution.

Orbital forcing of late Early Devonian storm events on a mixed carbonate-siliciclastic shelf, Longmenshan area, Sichuan Province, China

AbstractThe Yangmaba Formation of latest Early Devonian age in the Longmenshan area of Sichuan Province, China, is a shelfal facies that consists of four types of carbonate-siliciclastic deposits: clay-rich, siliciclastic sand-rich, carbonate-dominated, and hybrid mixed. Storm deposits vary in their thickness, composition, and abundance-per-meter within these mixed carbonate-siliciclastic deposits. Meter-scale statistics of the relative storm frequency (events-per-meter) and magnitude (bed thickness) were compiled in two coeval sections through each of the hybrid facies in the lower Yangmaba Formation, which spans approximately the entire conodont Polygnathus patulus Zone of the uppermost Emsian Stage. Low-pass filtering, spectral analysis, and Acycle software interpretation of these tempestite statistics yield 3.5 main oscillations in each section, with an average wavelength of ~23 m. These long-wavelength trends are semi-coincident with interpreted long-term variations in sea level, where shallower depths allowed a greater influence by storms. Superimposed on the long-wavelength cycles are medium-wavelength cycles of 5.5–6.3 m. The estimated ~1.5 m.y. time-span of this conodont zone of the lower Yangmaba Formation and the approximate 1:4 ratios of these wavelengths indicate that frequency and intensity of major storms and the recording of tempestites in the sedimentary record were modulated by ~100- and 95-k.y.-short-eccentricity orbital-climate oscillations superimposed on a main 405-k.y.-long-eccentricity cycle. These eccentricity climate cycles governed storm intensity and regional sea level on this margin of the tropical Yangtze Platform of South China.

Transient modeling and analysis of fractional-order resonant very high frequency boost converter

PurposeThis paper aims to present a simplified method to analyze the transient characteristics of a fractional-order very high frequency (VHF) resonant boost converter. The transient analytical solutions of state variables obtained by this method could be used as a guide for parameter design and circuit optimization.Design/methodology/approachThe VHF converter is decoupled into a simplified equivalent circuit model and described by the differential equation. The solution of the simplified equivalent circuit model is taken as the main oscillation component of the transient state variable. And the equivalent small parameter method (ESPM) and Kalman filter technology are used to solve the differential equation of the converter to obtain the steady-state ripple component. Then, by superimposing the abovementioned two parts, the approximate transient analytical solution can be acquired. Finally, the influence of the fractional order of the energy storage elements on the transient process of the converter is discussed.FindingsThe results from the proposed method agree well with those from simulations, which indicates that the proposed method can effectively analyze the transient characteristic of the fractional-order VHF converter, and the analytical solution derived from the proposed mathematical model shows sufficient accuracy.Originality/valueThis paper proposes for the first time a method to analyze the transient characteristics of a fractional-order VHF resonant boost converter. By combining the main oscillated solution derived from the simplified equivalent circuit model with the steady-state solution based on ESPM, this method can greatly reduce the computation amount to estimate the transient solution. In addition, the discussion on the order of fractional calculus of energy storage components can provide an auxiliary guidance for the selection of circuit parameters and the study of stability.