Energy storage systems(ESSs)operate as independent market participants and collaborate with photovoltaic(PV)generation units to enhance the flexible power supply capabilities of PV units.However,the dynamic variations...Energy storage systems(ESSs)operate as independent market participants and collaborate with photovoltaic(PV)generation units to enhance the flexible power supply capabilities of PV units.However,the dynamic variations in the profitability of ESSs in the electricity market are yet to be fully understood.This study introduces a dual-timescale dynamics model that integrates a spot market clearing(SMC)model into a system dynamics(SD)model to investigate the profit-aware capacity growth of ESSs and compares the profitability of independent energy storage systems(IESSs)with that of an ESS integrated within a PV(PV-ESS).Furthermore,this study aims to ascertain the optimal allocation of the PV-ESS.First,SD and SMC models were set up.Second,the SMC model simulated on an hourly timescale was incorporated into the SD model as a subsystem,a dual-timescale model was constructed.Finally,a development simulation and profitability analysis was conducted from 2022 to 2040 to reveal the dynamic optimal range of PV-ESS allocation.Additionally,negative electricity prices were considered during clearing processes.The simulation results revealed differences in profitability and capacity growth between IESS and PV-ESS,helping grid investors and policymakers to determine the boundaries of ESSs and dynamic optimal allocation of PV-ESSs.展开更多
The Huangsha-Tieshanlong quartz-vein tungsten polymetallic ore deposit, located in the northern Pangushan-Tieshanlong tungsten ore field in eastern Ganxian-Yudu prospecting areas of the Yushan metallogenic belt, is a ...The Huangsha-Tieshanlong quartz-vein tungsten polymetallic ore deposit, located in the northern Pangushan-Tieshanlong tungsten ore field in eastern Ganxian-Yudu prospecting areas of the Yushan metallogenic belt, is a well-known tungsten deposit in southern Jiangxi province, China. SHRIMP-determined dating of zircons from the Tieshanlong granite yields ages of 168.1±2.1 Ma （n=11, MSWD-1.3）. Rhenium and osmium isotopic dating of molybdenite from the Huangsha quartz-vein tungsten deposit determined by ICP-MS yields a weighted average ages of 153-3 Ma and model ages of 150.22.1 Ma - 155.4-2.3 Ma. The age of the Huangsha tungsten deposit is 10 to 15 Ma later than the Tieshanlong granite, which shows that there might have been another early Late Jurassic magmatic activity between 150 and 160 Ma, a process which is closely related with tungsten mineralization in this area. The Tieshanlong granite, the Hnangsha tungsten deposit and the Pangushan-Tieshanlong ore field were all formed around 150-170 Ma, belonging to products of a Mesozoic second large-scale mineralization. According to the collected molybdenite Re-Os dating results in southern Jiangxi province, the timescale of the associated molybdenum mineralization is 2-6 Ma in the tungsten deposit and the timescale of independent molybdenum mineralization is 1-4 Ma, implying the complexity of tungsten mineralization. Times of molybdenum mineralization are mainly concentrated in the Yanshanian, which includes three stages of 133-135 Ma, 150-162 Ma, and 166-170 Ma, respectively. The 150-162 Ma-stage is in accordance with ages of large-scale WoSn mineralization, which is mainly molybdenum mineralization characterized by associated molybdenum mineralization with development of an even greater-intensity independent molybdenum mineralization. Independent molybdenum mineralization occurred before and after large-scale W-Sn mineralization, which indicates that favorable prospecting period for molybdenum may be in Cretaceous and early late Jurassic.展开更多
To better understand the physical mechanism of the climate change on interdecadal-centennial timescale, this paper focuses on analysing and modelling the evolution characteristics of the climate change. The method of ...To better understand the physical mechanism of the climate change on interdecadal-centennial timescale, this paper focuses on analysing and modelling the evolution characteristics of the climate change. The method of wavelet transform is used to pick out the interdecadal timescale oscillations from long-term instrumental observations, natural proxy records, and modelling series. The modelling series derived from the most simplified nonlinear climatic model are used to identify whether modifications are concerned with some forcings such as the solar radiation on the climate system. The results show that two major oscillations exist in various observations and model series, namely the 20- 30a and the 60-70a timescale respectively, and these quasi-periodicities are modulated with time. Further, modelling results suggest that the originations of these oscillations are not directly linked with the periodic variation of solar radiations such as the 1-year cycle, the 11-year cycle, and others, but possibly induced by the internal nonlinear effects of the climate system. It seems that the future study on the genesis of the climate change with interdecadal-centennial timescale should focus on the internal nonlinear dynamics in the climate system.展开更多
A correlation analysis is performed to investigate the relationship between El Nino-Southern Oscillation （ENSO） and the Antarctic oscillation （AAO） at the quasi-quadrennial （QQ） timescale.It is found that the co...A correlation analysis is performed to investigate the relationship between El Nino-Southern Oscillation （ENSO） and the Antarctic oscillation （AAO） at the quasi-quadrennial （QQ） timescale.It is found that the cold tongue index （CTI） and the AAO index （AAOI） are negatively correlated with about a 7-month lead-time,while they are positively correlated with about a 15-month lag-time.To further explore this relationship,complex empirical orthogonal function analysis is employed in the QQ sea level pressure （SLP） anomalies from 1951 to 2002.The results indicate that,during the ENSO cycle,there exists one kind of global tropical wave of wavenumber 1 （GTW1） propagating eastward.With the traveling of GTW1,the tropical SLP anomaly tends to intrude into the southern mid-latitudes.Accordingly,three strong signals travel synchronously along the circumSouth-Pacific path,and a relatively weak signal extends eastward and poleward over the South Ocean in the Atlantic-Indian Ocean sector.Following the propagation of these signals,the AAO phase tends to be reversed progressively.As a result,there exists an evident lead-lag correlation between CTI and AAOI.It can be concluded that ENSO plays a key role in the phase transition of AAO at the QQ timescale.It is also noticed that this regular relationship is only evident in the canonical ENSO events,for which sea surface temperature （SST） anomalies extend westward from the tropical eastern Pacific.On the other hand,the similar relationships are not found among those atypical ENSO events for which SST anomalies spread eastward from the central Pacific,such as the 1982-1983 ENSO event.展开更多
A timescale decomposed threshold regression （TSDTR） downscaling approach to forecasting South China early summer rainfall （SCESR） is described by using long-term observed station rainfall data and NOAA ERSST data....A timescale decomposed threshold regression （TSDTR） downscaling approach to forecasting South China early summer rainfall （SCESR） is described by using long-term observed station rainfall data and NOAA ERSST data. It makes use of two distinct regression downscaling models corresponding to the interannual and interdecadal rainfall variability of SCESR. The two models are developed based on the partial least squares （PLS） regression technique, linking SCESR to SST modes in preceding months on both interannual and interdecadal timescales. Specifically, using the datasets in the calibration period 1915-84, the variability of SCESR and SST are decomposed into interannual and interdecadal components. On the interannual timescale, a threshold PLS regression model is fitted to interannual components of SCESR and March SST patterns by taking account of the modulation of negative and positive phases of the Pacific Decadal Oscillation （PDO）. On the interdecadal timescale, a standard PLS regression model is fitted to the relationship between SCESR and preceding November SST patterns. The total rainfall prediction is obtained by the sum of the outputs from both the interannual and interdecadal models. Results show that the TSDTR downscaling approach achieves reasonable skill in predicting the observed rainfall in the validation period 1985-2006, compared to other simpler approaches. This study suggests that the TSDTR approach, considering different interannual SCESR-SST relationships under the modulation of PDO phases, as well as the interdecadal variability of SCESR associated with SST patterns, may provide a new perspective to improve climate predictions.展开更多
Part II of this study detects the dominant decadal-centennial timescales in four SST indices up to the 2010/2011 winter and tries to relate them to the observed 11-yr and 88-yr solar activity with the sunspot number u...Part II of this study detects the dominant decadal-centennial timescales in four SST indices up to the 2010/2011 winter and tries to relate them to the observed 11-yr and 88-yr solar activity with the sunspot number up to Solar Cycle 24. To explore plausible solar origins of the observed decadal-centennial timescales in the SSTs and climate variability in general, we design a simple one-dimensional dynamical system forced by an annual cycle modulated by a small-amplitude single- or multi-scale ＂solar activity.＂ Results suggest that nonlinear harmonic and subharmonic resonance of the system to the forcing and period-doubling bifurcations are responsible for the dominant timescales in the system, including the 60-yr timescale that dominates the Atlantic Multidecadal Oscillation. The dominant timescales in the forced system depend on the system＇s parameter setting. Scale enhancement among the dominant response timescales may result in dramatic amplifications over a few decades and extreme values of the time series on various timescales. Three possible energy sources for such amplifications and extremes are proposed. Dynamical model results suggest that solar activity may play an important yet not well recognized role in the observed decadal-centennial climate variability. The atmospheric dynamical amplifying mechanism shown in Part I and the nonlinear resonant and bifurcation mechanisms shown in Part II help us to understand the solar source of the multi-scale climate change in the 20th century and the fact that different solar influenced dominant timescales for recurrent climate extremes for a given region or a parameter setting. Part II also indicates that solar influences on climate cannot be linearly compared with non-cyclic or sporadic thermal forcings because they cannot exert their influences on climate in the same way as the sun does.展开更多
1.Introduction One of the major challenges in Geoscience is to understand how the formation and evolution of the Earth System are governed by timescales-that is,how the various geological processes that continue to co...1.Introduction One of the major challenges in Geoscience is to understand how the formation and evolution of the Earth System are governed by timescales-that is,how the various geological processes that continue to contribute to its present-day structure and composition operated in the deep past.The traditional view of such processes refers to events that occur at immense spatial scales and over hundreds of millions of years,constrained in most cases by the ages of rocks determined using isotopic dating methods or the fossil record.However,the modern view of geological processes has increasingly acknowledged that their durations can be significantly shorter than previously thought possible,or indeed detectable without recent analytical innovations.Earthquakes are a prime example of rapid,high energy and episodic events that have a profound effect on subsequent processes such as metamorphism,fluid transport,and ore formation e the evidence of which is written in microstructures,compositional zoning,and P-T records.Experimental studies have also revealed that the reaction rates between fluids and rocks can be extremely rapid relative to geological timescales.This has led to the notion that geological processes are not necessarily continuous over millions of years but may,in fact,be sporadic,with long periods where essentially no reactions take place punctuated by periods of intense activity.展开更多
Using NCEP/NCAR R2 reanalysis daily data and daily meteorologicalobservational data of southwest China in 2010, this paper studied the submonthlytimescale oscillation characteristics of the East Asian winter monsoon (...Using NCEP/NCAR R2 reanalysis daily data and daily meteorologicalobservational data of southwest China in 2010, this paper studied the submonthlytimescale oscillation characteristics of the East Asian winter monsoon (EAWM) and itseffect on the temperature of southwest China in 2010 by bandpass filtering, wavelettransformation, composite analysis and correlation analysis. The main conclusions areas follows: The EAWM in 2010 was dominated by low-frequency oscillations of about 7-,12-, and 30-day periods. There existed obviously negative correlation between theEAWM and the winter temperature in southwest China on submonthly, quasi-weeklyand quasi-biweekly timescales, and negative correlation was more obvious on thequasi-biweekly than the quasi-weekly timescale. There was significant difference in thedistribution of high, middle and low layer of the troposphere when the EAWM was onthe submonthly, quasi-one-week and quasi-two-week timescales in the positive andnegative phase. In the positive EAWM phase, the upper-level subtropical westerly jet isstronger and the East Asia trough is deeper, thus it is favorable for the dominance ofmore powerful north wind and lower temperature in southwest China. On the contrary,in the negative EAWM phase, the upper-level subtropical westerly jet is weaker and theEast Asia trough is shallower, thus unfavorable for the north wind and lowertemperature in southwest China.展开更多
New integrative stratigraphy and timescales for 13 geological periods in China from the Ediacaran to the Quaternary have recently been published in a special issue of SCIENCE CHINA Earth Sciences.The research summariz...New integrative stratigraphy and timescales for 13 geological periods in China from the Ediacaran to the Quaternary have recently been published in a special issue of SCIENCE CHINA Earth Sciences.The research summarizes the latest advances in stratigraphy and timescale as well as discusses the correlation among different blocks in China and with international timescales.展开更多
The increasing trend for integrating renewable energy sources into the grid to achieve a cleaner energy system is one of the main reasons for the development of sustainable microgrid(MG)technologies.As typical power-e...The increasing trend for integrating renewable energy sources into the grid to achieve a cleaner energy system is one of the main reasons for the development of sustainable microgrid(MG)technologies.As typical power-electronized power systems,MGs make extensive use of power electronics converters,which are highly controllable and flexible but lead to a profound impact on the dynamic performance of the whole system.Compared with traditional large-capacity power systems,MGs are less resistant to perturbations,and various dynamic variables are coupled with each other on multiple timescales,resulting in a more complex system instability mechanism.To meet the technical and economic challenges,such as active and reactive power-sharing,voltage,and frequency deviations,and imbalances between power supply and demand,the concept of hierarchical control has been introduced into MGs,allowing systems to control and manage the high capacity of renewable energy sources and loads.However,as the capacity and scale of the MG system increase,along with a multi-timescale control loop design,the multi-timescale interactions in the system may become more significant,posing a serious threat to its safe and stable operation.To investigate the multi-timescale behaviors and instability mechanisms under dynamic inter-actions for AC MGs,existing coordinated control strategies are discussed,and the dynamic stability of the system is defined and classified in this paper.Then,the modeling and assessment methods for the stability analysis of multi-timescale systems are also summarized.Finally,an outlook and discussion of future research directions for AC MGs are also presented.展开更多
The intrinsic neural timescale(INT)provides temporal windows in brain activity that process information of different durations,crucial for the integration and segregation of external inputs and ultimately shaping cogn...The intrinsic neural timescale(INT)provides temporal windows in brain activity that process information of different durations,crucial for the integration and segregation of external inputs and ultimately shaping cognition and behavior.Recent research has uncovered a pronounced INT hierarchy along the adult hippocampus's longaxis.Yet,the development of INT organization within the hippocampus—particularly the pattern of its hierarchical structure and its impact on cognitive development—has not been thoroughly investigated in youth.Here,we discovered that the INT distribution in youth presents a distinct hierarchical structure along both posterioranterior and proximal-distal axes of the hippocampus.Strikingly,this hierarchical structure correlates signifi-cantly with the first principal gradient of the hippocampal-cortical functional connectome and the thickness of hippocampal grey matter.Furthermore,we observed notable changes in the hippocampal INT landscape during youth,characterized by a general narrowing of timescales,alongside dedifferentiation along the hippocampal organizational axes.These maturational changes significantly link to improvements in inhibitory control and working memory performance.Collectively,our findings reveal the developmental patterns of temporal integration and segregation hierarchies within hippocampus,and highlights the profound significance of INT as a neural underpinning that orchestrates cognitive growth.展开更多
In a high-profile vote in March 2024,an international scientific committee chose not to support designating a new geological epoch,the Anthropocene[1].Prior to this somewhat unexpected decision,scientists spent 15 yea...In a high-profile vote in March 2024,an international scientific committee chose not to support designating a new geological epoch,the Anthropocene[1].Prior to this somewhat unexpected decision,scientists spent 15 years gathering abundant evidence for a shift in the geological timescale that would acknowledge humankind’s accelerating impact on the Earth,which they argued has already left a distinctive mark in the planet’s geological strata.While some will continue to work for formal recognition of the Anthropocene Epoch,others say the concept remains useful whether it is integrated into the official geological time scale or not[2].展开更多
The factors controlling dust activity and humidity in Central Asia and their relationships remain controversial,partly due to a lack of high-resolution geological records for the mid-to-late last glaciation.In this st...The factors controlling dust activity and humidity in Central Asia and their relationships remain controversial,partly due to a lack of high-resolution geological records for the mid-to-late last glaciation.In this study,we established an optically stimulated luminescence chronology for the QSHA profile in the Yili Basin,a region influenced by westerlies.Grain size and trace element data were used as paleoclimatic indicators.We investigated the relationships among Central Asian dust activity,humidity,and westerlies strength on orbital to millennial scale from 37.4 ka to 11.6 ka.Our study reveals that,on orbital timescales,humidity is positively correlated with westerlies strength which controlled by precession.Dust activity is controlled by Siberian High which was regulated by Northern Hemisphere high-latitude temperature.Their responses to low-latitude and high-latitude forcing mechanisms respectively and present an opposite relationship.On millennial timescales,humidity and westerlies strength are positively correlated.During Marine Isotope Stage(MIS)2,humidity and dust activity show synchronous fluctuations,while during MIS 3,they exhibit an inverse relationship.Westerlies strength regulated humidity,which subsequently controlled glacial activity in the Tianshan Mountains,influencing dust activity in Central Asia.Additionally,the QSHA profile recorded seven Dansgaard-Oeschger(D-O)events on millennial timescales,indicating a potential link between Central Asian dust activity and high-latitude temperature variations in the Northern Hemisphere.Our findings provide new insights into dust and humidity interaction during the last glaciation periods in Central Asia and contribute to understanding global dust and hydrological cycles.展开更多
Evaporation plays an important role in water balance on the land surface. In Northern China, the evaporation series of the recent 115 years was reconstructed on the basis of Yhornthwaite evaporation formula. The chara...Evaporation plays an important role in water balance on the land surface. In Northern China, the evaporation series of the recent 115 years was reconstructed on the basis of Yhornthwaite evaporation formula. The characteristics of the reconstructed series were analyzed using 10-year running mean filter, power spectrum method, and running t-text of abrupt changes on the paper. The results showed that there were remarkable interannual fluctuations with timescales of about quasi-8-year, 3-4-year, and quasi-2-year, and interdecadal oscillations with timescales of 57.5-year, quasi-23-year, and l l.5-year. Meanwhile, the abrupt changes of the evaporation series were also of interdecadal timescale. Either interannual fluctuations or interdecadal oscillations of evaporation were closely related to variations in air temperatures and precipitation.展开更多
A series of global major geological and biological events occurred during the Permian Period. Establishing a highresolution stratigraphic and temporal framework is essential to understand their cause-effect relationsh...A series of global major geological and biological events occurred during the Permian Period. Establishing a highresolution stratigraphic and temporal framework is essential to understand their cause-effect relationship. The official International timescale of the Permian System consists of three series(i.e., Cisuralian, Guadalupian and Lopingian in ascending order) and nine stages. In China, the Permian System is composed of three series(Chuanshanian, Yansingian and Lopingian) and eight stages, of which the subdivisions and definitions of the Chuanshanian and Yangsingian series are very different from the Cisuralian and Guadalupian series. The Permian Period spanned ～47 Myr. Its base is defined by the First Appearance Datum(FAD) of the conodont Streptognathodus isolatus at Aidaralash, Kazakhstan with an interpolated absolute age 298.9±0.15 Ma at Usolka, southern Urals, Russia. Its top equals the base of the Triassic System and is defined by the FAD of the conodont Hindeodus parvus at Meishan D section, southeast China with an interpolated absolute age 251.902±0.024 Ma. Thirty-five conodont, 23 fusulinid, 17 radiolarian and 20 ammonoid zones are established for the Permian in China, of which the Guadalupian and Lopingian conodont zones have been served as the standard for international correlation. The Permian δ13 Ccarbtrend indicates that it is characterized by a rapid negative shift of 3–5‰ at the end of the Changhsingian, which can be used for global correlation of the end-Permian mass extinction interval, but δ13 Ccarbrecords from all other intervals may have more or less suffered subsequent diagenetic alteration or represented regional or local signatures only. Permian δ18 Oapatitestudies suggest that an icehouse stage dominated the time interval from the late Carboniferous to Kungurian(late Cisuralian). However, paleoclimate began to ameriolate during the late Kungurian and gradually shifted into a greenhouse-dominated stage during the Guadalupian.The Changhsingian was a relatively cool stage, followed by a globally-recognizable rapid temperature rise of 8–10°C at the very end of the Changhsingian. The87 Sr/86 Sr ratio trend shows that their values at the beginning of the Permian were between 0.70800,then gradually decreased to the late Capitanian minimum 0.70680–0.70690, followed by a persistent increase until the end of the Permian with the value 0.70708. Magenetostratigraphy suggests two distinct stages separated by the Illawarra Reversal in the middle Wordian, of which the lower is the reverse polarity Kiaman Superchron and the upper is the mixed-polarity Illawarra Superchron. The end-Guadalupian(or pre-Lopingian) biological crisis occurred during the late Capitanian, when faunal changeovers of different fossil groups had different paces, but generally experienced a relatively long time from the Jinogondolella altudensis Zone until the earliest Wuchiapingian. The end-Permian mass extinction was a catastrophic event that is best constrained at the Meishan section, which occurred at 251.941±0.037 Ma and persisted no more than 61±48 kyr. After the major pulse at Bed 25, the extinction patterns are displayed differently in different sections. The global end-Guadalupian regression is manifested between the conodont Jinogondolella xuanhanensis and Clarkina dukouensis zones and the endChanghsingian transgression began in the Hindeodus changxingensis-Clarkina zhejiangensis Zone. The Permian Period is also characterized by strong faunal provincialism in general, which resulted in difficulties in inter-continental and inter-regional correlation of both marine and terrestrial systems.展开更多
The Serling Co region is located at the transitional zone of the interaction between the Indian monsoon and the westerlies over the Tibetan Plateau. The Serling Co lake covers a water area of2,389 km2(June 2017) in a ...The Serling Co region is located at the transitional zone of the interaction between the Indian monsoon and the westerlies over the Tibetan Plateau. The Serling Co lake covers a water area of2,389 km2(June 2017) in a 45,530 km2drainage basin. Under the dramatic hydro-meteorological changes on the Tibetan Plateau in recent decades, and complex hydrological compositions of rivers and lakes in the basin, the lake area expanded by 43%, from1,667 km2in 1976, to 2,389 km2in 2017 (1)In 2014 it surpassed Nam Co as the largest lake on the Tibetan Plateau [2], and exerts significant effect on regional environmental conditions.展开更多
Stability of grid-connected VSCs in DC voltage control(DVC)timescales(i.e.,the frequency range of dynamics covering converter outer controls)has recently caught increased attention,while the existing approaches,such a...Stability of grid-connected VSCs in DC voltage control(DVC)timescales(i.e.,the frequency range of dynamics covering converter outer controls)has recently caught increased attention,while the existing approaches,such as eigenvalue analysis and dq-domain impedance analysis,have respective limitations on addressing these types of stability issues.This paper proposes an alternative net damping criterion dedicated for analyzing the DVC timescale stability in a multi-VSC system.This criterion is strictly mapped from the Nyquist stability criterion utilizing the gain margin concept,which preserves the advantages of the classical positive net damping criterion suggested by Canay[20]–allowing for decomposition analysis of a subsystem’s contribution to the closed-loop stability in a single-input single-output(SISO)framework,but overcomes its deficiency of possibly erroneous prediction of system dynamic behaviors.Case studies show that the proposed criterion can correctly predict some unstable conditions(e.g.,monotonic divergence)which cannot be identified by the classical net damping criterion.Additionally,the condition for when the classical criterion is available is also pointed out,the proposed criterion can also act as a complement of the classical criterion for stability examination.展开更多
An equivalent source-load MTDC system including DC voltage control units,power control units and interconnected DC lines is considered in this paper,which can be regarded as a generic structure of low-voltage DC micro...An equivalent source-load MTDC system including DC voltage control units,power control units and interconnected DC lines is considered in this paper,which can be regarded as a generic structure of low-voltage DC microgrids,mediumvoltage DC distribution systems or HVDC transmission systems with a common DC bus.A reduced-order model is proposed with a circuit structure of a resistor,inductor and capacitor in parallel for dynamic stability analysis of the system in DC voltage control timescale.The relationship between control parameters and physical parameters of the equivalent circuit can be found,which provides an intuitive insight into the physical meaning of control parameters.Employing this model,a second-order characteristic equation is further derived to investigate system dynamic stability mechanisms in an analytical approach.As a result,the system oscillation frequency and damping are characterized in a straight forward manner,and the role of electrical and control parameters and different system-level control strategies in system dynamic stability in DC voltage control timescale is defined.The effectiveness of the proposed reduced-order model and the correctness of the theoretical analysis are verified by simulation based on PSCAD/EMTDC and an experiment based on a hardware low-voltage MTDC system platform.展开更多
This paper deals with how the purely mathematical approach can be used to solve transient-state instability problems of dissolution-timescale reactive infiltration(DTRI) in fluid-saturated porous rocks. Three key step...This paper deals with how the purely mathematical approach can be used to solve transient-state instability problems of dissolution-timescale reactive infiltration(DTRI) in fluid-saturated porous rocks. Three key steps involved in such an approach are:(1) to mathematically derive an analytical solution(known as the base solution or conventional solution) for a quasi-steady state problem of the dissolution timescale, which is viewed as a frozen state of the original transient-state instability problem;(2)to mathematically deduce a group of first-order perturbation partial-differential equations(PDEs) for the quasi-steady state problem;(3) to mathematically derive an analytical solution(known as the perturbation solution or unconventional solution) for this group of first-order perturbation PDEs. Because of difficulty in mathematically solving a transient-state instability problem of DTRI in general cases, only a special case, in which some nonlinear coupling between governing PDEs of the problem can be decoupled, is considered to illustrate these three key steps in this study. The related theoretical results demonstrated that the transient chemical dissolution front can become unstable in the DTRI system of large Zh numbers when the long wavelength perturbations are applied to the system. This new finding may lay the theoretical foundation for developing innovative technique to exploit shale gas resources in the deep Earth.展开更多
Using molecular dynamics simulations, we show that free diffusion of a nanoscale particle (molecule) with asymmetric structure critically depends on the orientation in a finite timescale of picoseconds to nanoseconds....Using molecular dynamics simulations, we show that free diffusion of a nanoscale particle (molecule) with asymmetric structure critically depends on the orientation in a finite timescale of picoseconds to nanoseconds. In a timescale of ~100 ps, there are ~10% more possibilities for the particle moving along the initial orientation than moving opposite to the orientation; and the diffusion distances of the particle reach ~1 nm. We find that the key to this observation is the orientation-dependence of the damping force to the moving of the nanoscale particle and a finite time is required to regulate the particle orientation. This finding extends the work of Einstein to nano-world beyond random Brownian motion, thus will have a critical role in the understanding of the nanoscale world.展开更多
基金supported by National Natural Science Foundation of China(U2066209)。
文摘Energy storage systems(ESSs)operate as independent market participants and collaborate with photovoltaic(PV)generation units to enhance the flexible power supply capabilities of PV units.However,the dynamic variations in the profitability of ESSs in the electricity market are yet to be fully understood.This study introduces a dual-timescale dynamics model that integrates a spot market clearing(SMC)model into a system dynamics(SD)model to investigate the profit-aware capacity growth of ESSs and compares the profitability of independent energy storage systems(IESSs)with that of an ESS integrated within a PV(PV-ESS).Furthermore,this study aims to ascertain the optimal allocation of the PV-ESS.First,SD and SMC models were set up.Second,the SMC model simulated on an hourly timescale was incorporated into the SD model as a subsystem,a dual-timescale model was constructed.Finally,a development simulation and profitability analysis was conducted from 2022 to 2040 to reveal the dynamic optimal range of PV-ESS allocation.Additionally,negative electricity prices were considered during clearing processes.The simulation results revealed differences in profitability and capacity growth between IESS and PV-ESS,helping grid investors and policymakers to determine the boundaries of ESSs and dynamic optimal allocation of PV-ESSs.
基金supported jointly by grants No K1 022K0901 from the Scientific Research Fund of the China Central Non-Commercial Institutegrant No 40772063 from the National Natural Science Foundation of Chinathe Programme of Excellent Young Scientists of the Ministry of Land and Resources and Geological Survey Program Grant 1212010561603-2 from the China Geological Survey
文摘The Huangsha-Tieshanlong quartz-vein tungsten polymetallic ore deposit, located in the northern Pangushan-Tieshanlong tungsten ore field in eastern Ganxian-Yudu prospecting areas of the Yushan metallogenic belt, is a well-known tungsten deposit in southern Jiangxi province, China. SHRIMP-determined dating of zircons from the Tieshanlong granite yields ages of 168.1±2.1 Ma （n=11, MSWD-1.3）. Rhenium and osmium isotopic dating of molybdenite from the Huangsha quartz-vein tungsten deposit determined by ICP-MS yields a weighted average ages of 153-3 Ma and model ages of 150.22.1 Ma - 155.4-2.3 Ma. The age of the Huangsha tungsten deposit is 10 to 15 Ma later than the Tieshanlong granite, which shows that there might have been another early Late Jurassic magmatic activity between 150 and 160 Ma, a process which is closely related with tungsten mineralization in this area. The Tieshanlong granite, the Hnangsha tungsten deposit and the Pangushan-Tieshanlong ore field were all formed around 150-170 Ma, belonging to products of a Mesozoic second large-scale mineralization. According to the collected molybdenite Re-Os dating results in southern Jiangxi province, the timescale of the associated molybdenum mineralization is 2-6 Ma in the tungsten deposit and the timescale of independent molybdenum mineralization is 1-4 Ma, implying the complexity of tungsten mineralization. Times of molybdenum mineralization are mainly concentrated in the Yanshanian, which includes three stages of 133-135 Ma, 150-162 Ma, and 166-170 Ma, respectively. The 150-162 Ma-stage is in accordance with ages of large-scale WoSn mineralization, which is mainly molybdenum mineralization characterized by associated molybdenum mineralization with development of an even greater-intensity independent molybdenum mineralization. Independent molybdenum mineralization occurred before and after large-scale W-Sn mineralization, which indicates that favorable prospecting period for molybdenum may be in Cretaceous and early late Jurassic.
文摘To better understand the physical mechanism of the climate change on interdecadal-centennial timescale, this paper focuses on analysing and modelling the evolution characteristics of the climate change. The method of wavelet transform is used to pick out the interdecadal timescale oscillations from long-term instrumental observations, natural proxy records, and modelling series. The modelling series derived from the most simplified nonlinear climatic model are used to identify whether modifications are concerned with some forcings such as the solar radiation on the climate system. The results show that two major oscillations exist in various observations and model series, namely the 20- 30a and the 60-70a timescale respectively, and these quasi-periodicities are modulated with time. Further, modelling results suggest that the originations of these oscillations are not directly linked with the periodic variation of solar radiations such as the 1-year cycle, the 11-year cycle, and others, but possibly induced by the internal nonlinear effects of the climate system. It seems that the future study on the genesis of the climate change with interdecadal-centennial timescale should focus on the internal nonlinear dynamics in the climate system.
基金The Major National Scientific Research Project on Global Change under contract No.2010CB951901the National Science Foundation of China under contract No.40821092Special Fund for Public Welfare Industry (Meteorology) under contract No.GYHY200906018
文摘A correlation analysis is performed to investigate the relationship between El Nino-Southern Oscillation （ENSO） and the Antarctic oscillation （AAO） at the quasi-quadrennial （QQ） timescale.It is found that the cold tongue index （CTI） and the AAO index （AAOI） are negatively correlated with about a 7-month lead-time,while they are positively correlated with about a 15-month lag-time.To further explore this relationship,complex empirical orthogonal function analysis is employed in the QQ sea level pressure （SLP） anomalies from 1951 to 2002.The results indicate that,during the ENSO cycle,there exists one kind of global tropical wave of wavenumber 1 （GTW1） propagating eastward.With the traveling of GTW1,the tropical SLP anomaly tends to intrude into the southern mid-latitudes.Accordingly,three strong signals travel synchronously along the circumSouth-Pacific path,and a relatively weak signal extends eastward and poleward over the South Ocean in the Atlantic-Indian Ocean sector.Following the propagation of these signals,the AAO phase tends to be reversed progressively.As a result,there exists an evident lead-lag correlation between CTI and AAOI.It can be concluded that ENSO plays a key role in the phase transition of AAO at the QQ timescale.It is also noticed that this regular relationship is only evident in the canonical ENSO events,for which sea surface temperature （SST） anomalies extend westward from the tropical eastern Pacific.On the other hand,the similar relationships are not found among those atypical ENSO events for which SST anomalies spread eastward from the central Pacific,such as the 1982-1983 ENSO event.
基金sponsored by the National Basic Research Program of China (Grant No. 2012CB955202)the China Scholarship Council under the Joint-PhD program for conducting research at CSIROsupported by the Indian Ocean Climate Initiative
文摘A timescale decomposed threshold regression （TSDTR） downscaling approach to forecasting South China early summer rainfall （SCESR） is described by using long-term observed station rainfall data and NOAA ERSST data. It makes use of two distinct regression downscaling models corresponding to the interannual and interdecadal rainfall variability of SCESR. The two models are developed based on the partial least squares （PLS） regression technique, linking SCESR to SST modes in preceding months on both interannual and interdecadal timescales. Specifically, using the datasets in the calibration period 1915-84, the variability of SCESR and SST are decomposed into interannual and interdecadal components. On the interannual timescale, a threshold PLS regression model is fitted to interannual components of SCESR and March SST patterns by taking account of the modulation of negative and positive phases of the Pacific Decadal Oscillation （PDO）. On the interdecadal timescale, a standard PLS regression model is fitted to the relationship between SCESR and preceding November SST patterns. The total rainfall prediction is obtained by the sum of the outputs from both the interannual and interdecadal models. Results show that the TSDTR downscaling approach achieves reasonable skill in predicting the observed rainfall in the validation period 1985-2006, compared to other simpler approaches. This study suggests that the TSDTR approach, considering different interannual SCESR-SST relationships under the modulation of PDO phases, as well as the interdecadal variability of SCESR associated with SST patterns, may provide a new perspective to improve climate predictions.
基金provided by the LASG State Key Laboratory Special Fund for this research project
文摘Part II of this study detects the dominant decadal-centennial timescales in four SST indices up to the 2010/2011 winter and tries to relate them to the observed 11-yr and 88-yr solar activity with the sunspot number up to Solar Cycle 24. To explore plausible solar origins of the observed decadal-centennial timescales in the SSTs and climate variability in general, we design a simple one-dimensional dynamical system forced by an annual cycle modulated by a small-amplitude single- or multi-scale ＂solar activity.＂ Results suggest that nonlinear harmonic and subharmonic resonance of the system to the forcing and period-doubling bifurcations are responsible for the dominant timescales in the system, including the 60-yr timescale that dominates the Atlantic Multidecadal Oscillation. The dominant timescales in the forced system depend on the system＇s parameter setting. Scale enhancement among the dominant response timescales may result in dramatic amplifications over a few decades and extreme values of the time series on various timescales. Three possible energy sources for such amplifications and extremes are proposed. Dynamical model results suggest that solar activity may play an important yet not well recognized role in the observed decadal-centennial climate variability. The atmospheric dynamical amplifying mechanism shown in Part I and the nonlinear resonant and bifurcation mechanisms shown in Part II help us to understand the solar source of the multi-scale climate change in the 20th century and the fact that different solar influenced dominant timescales for recurrent climate extremes for a given region or a parameter setting. Part II also indicates that solar influences on climate cannot be linearly compared with non-cyclic or sporadic thermal forcings because they cannot exert their influences on climate in the same way as the sun does.
文摘1.Introduction One of the major challenges in Geoscience is to understand how the formation and evolution of the Earth System are governed by timescales-that is,how the various geological processes that continue to contribute to its present-day structure and composition operated in the deep past.The traditional view of such processes refers to events that occur at immense spatial scales and over hundreds of millions of years,constrained in most cases by the ages of rocks determined using isotopic dating methods or the fossil record.However,the modern view of geological processes has increasingly acknowledged that their durations can be significantly shorter than previously thought possible,or indeed detectable without recent analytical innovations.Earthquakes are a prime example of rapid,high energy and episodic events that have a profound effect on subsequent processes such as metamorphism,fluid transport,and ore formation e the evidence of which is written in microstructures,compositional zoning,and P-T records.Experimental studies have also revealed that the reaction rates between fluids and rocks can be extremely rapid relative to geological timescales.This has led to the notion that geological processes are not necessarily continuous over millions of years but may,in fact,be sporadic,with long periods where essentially no reactions take place punctuated by periods of intense activity.
文摘Using NCEP/NCAR R2 reanalysis daily data and daily meteorologicalobservational data of southwest China in 2010, this paper studied the submonthlytimescale oscillation characteristics of the East Asian winter monsoon (EAWM) and itseffect on the temperature of southwest China in 2010 by bandpass filtering, wavelettransformation, composite analysis and correlation analysis. The main conclusions areas follows: The EAWM in 2010 was dominated by low-frequency oscillations of about 7-,12-, and 30-day periods. There existed obviously negative correlation between theEAWM and the winter temperature in southwest China on submonthly, quasi-weeklyand quasi-biweekly timescales, and negative correlation was more obvious on thequasi-biweekly than the quasi-weekly timescale. There was significant difference in thedistribution of high, middle and low layer of the troposphere when the EAWM was onthe submonthly, quasi-one-week and quasi-two-week timescales in the positive andnegative phase. In the positive EAWM phase, the upper-level subtropical westerly jet isstronger and the East Asia trough is deeper, thus it is favorable for the dominance ofmore powerful north wind and lower temperature in southwest China. On the contrary,in the negative EAWM phase, the upper-level subtropical westerly jet is weaker and theEast Asia trough is shallower, thus unfavorable for the north wind and lowertemperature in southwest China.
基金supported by the National Natural Science Foundation of Chinathe Strategic Priority Research Program(B) and the Key Research Program of Frontier Sciences of the Chinese Academy of Sciences
文摘New integrative stratigraphy and timescales for 13 geological periods in China from the Ediacaran to the Quaternary have recently been published in a special issue of SCIENCE CHINA Earth Sciences.The research summarizes the latest advances in stratigraphy and timescale as well as discusses the correlation among different blocks in China and with international timescales.
基金partly supported by the National Natural Science Foundation of China(NSFC)(No.51977026)the Science and Technology Program of Sichuan Province(No.2021YFG0255)the Sichuan Pro-vincial Postdoctoral Science Foundation(No.246861).
文摘The increasing trend for integrating renewable energy sources into the grid to achieve a cleaner energy system is one of the main reasons for the development of sustainable microgrid(MG)technologies.As typical power-electronized power systems,MGs make extensive use of power electronics converters,which are highly controllable and flexible but lead to a profound impact on the dynamic performance of the whole system.Compared with traditional large-capacity power systems,MGs are less resistant to perturbations,and various dynamic variables are coupled with each other on multiple timescales,resulting in a more complex system instability mechanism.To meet the technical and economic challenges,such as active and reactive power-sharing,voltage,and frequency deviations,and imbalances between power supply and demand,the concept of hierarchical control has been introduced into MGs,allowing systems to control and manage the high capacity of renewable energy sources and loads.However,as the capacity and scale of the MG system increase,along with a multi-timescale control loop design,the multi-timescale interactions in the system may become more significant,posing a serious threat to its safe and stable operation.To investigate the multi-timescale behaviors and instability mechanisms under dynamic inter-actions for AC MGs,existing coordinated control strategies are discussed,and the dynamic stability of the system is defined and classified in this paper.Then,the modeling and assessment methods for the stability analysis of multi-timescale systems are also summarized.Finally,an outlook and discussion of future research directions for AC MGs are also presented.
基金Shuyu Li is supported by the National Natural Science Foundation of China(32271146)the Startup Funds for Top-notch Talents at Beijing Normal University。
文摘The intrinsic neural timescale(INT)provides temporal windows in brain activity that process information of different durations,crucial for the integration and segregation of external inputs and ultimately shaping cognition and behavior.Recent research has uncovered a pronounced INT hierarchy along the adult hippocampus's longaxis.Yet,the development of INT organization within the hippocampus—particularly the pattern of its hierarchical structure and its impact on cognitive development—has not been thoroughly investigated in youth.Here,we discovered that the INT distribution in youth presents a distinct hierarchical structure along both posterioranterior and proximal-distal axes of the hippocampus.Strikingly,this hierarchical structure correlates signifi-cantly with the first principal gradient of the hippocampal-cortical functional connectome and the thickness of hippocampal grey matter.Furthermore,we observed notable changes in the hippocampal INT landscape during youth,characterized by a general narrowing of timescales,alongside dedifferentiation along the hippocampal organizational axes.These maturational changes significantly link to improvements in inhibitory control and working memory performance.Collectively,our findings reveal the developmental patterns of temporal integration and segregation hierarchies within hippocampus,and highlights the profound significance of INT as a neural underpinning that orchestrates cognitive growth.
文摘In a high-profile vote in March 2024,an international scientific committee chose not to support designating a new geological epoch,the Anthropocene[1].Prior to this somewhat unexpected decision,scientists spent 15 years gathering abundant evidence for a shift in the geological timescale that would acknowledge humankind’s accelerating impact on the Earth,which they argued has already left a distinctive mark in the planet’s geological strata.While some will continue to work for formal recognition of the Anthropocene Epoch,others say the concept remains useful whether it is integrated into the official geological time scale or not[2].
基金supported by the Natural Science Foundation of China(Grant Nos.42372220,42172207)the Youth Innovation Promotion Association Chinese Academy of Sciences(Grant No.Y2022102)+1 种基金the Science and Technology Innovation Project of Laoshan Laboratory(Grant No.LSKJ202203300)the International Partnership Program of the Chinese Academy of Sciences.
文摘The factors controlling dust activity and humidity in Central Asia and their relationships remain controversial,partly due to a lack of high-resolution geological records for the mid-to-late last glaciation.In this study,we established an optically stimulated luminescence chronology for the QSHA profile in the Yili Basin,a region influenced by westerlies.Grain size and trace element data were used as paleoclimatic indicators.We investigated the relationships among Central Asian dust activity,humidity,and westerlies strength on orbital to millennial scale from 37.4 ka to 11.6 ka.Our study reveals that,on orbital timescales,humidity is positively correlated with westerlies strength which controlled by precession.Dust activity is controlled by Siberian High which was regulated by Northern Hemisphere high-latitude temperature.Their responses to low-latitude and high-latitude forcing mechanisms respectively and present an opposite relationship.On millennial timescales,humidity and westerlies strength are positively correlated.During Marine Isotope Stage(MIS)2,humidity and dust activity show synchronous fluctuations,while during MIS 3,they exhibit an inverse relationship.Westerlies strength regulated humidity,which subsequently controlled glacial activity in the Tianshan Mountains,influencing dust activity in Central Asia.Additionally,the QSHA profile recorded seven Dansgaard-Oeschger(D-O)events on millennial timescales,indicating a potential link between Central Asian dust activity and high-latitude temperature variations in the Northern Hemisphere.Our findings provide new insights into dust and humidity interaction during the last glaciation periods in Central Asia and contribute to understanding global dust and hydrological cycles.
基金Project supported by the Ministry of Science and Technology in China (Grant No: 2002DIB20067)
文摘Evaporation plays an important role in water balance on the land surface. In Northern China, the evaporation series of the recent 115 years was reconstructed on the basis of Yhornthwaite evaporation formula. The characteristics of the reconstructed series were analyzed using 10-year running mean filter, power spectrum method, and running t-text of abrupt changes on the paper. The results showed that there were remarkable interannual fluctuations with timescales of about quasi-8-year, 3-4-year, and quasi-2-year, and interdecadal oscillations with timescales of 57.5-year, quasi-23-year, and l l.5-year. Meanwhile, the abrupt changes of the evaporation series were also of interdecadal timescale. Either interannual fluctuations or interdecadal oscillations of evaporation were closely related to variations in air temperatures and precipitation.
基金supported by the Strategic Priority Research Program (B) (Grant Nos. XDB18000000, XDB26000000)Key Research Program of Frontier Sciences from the Chinese Academy of Sciences (Grant No. QYZDY-SSW-DQC023)the National Natural Science Foundation of China (Grant Nos. 41290260, 41420104003, U1702242)
文摘A series of global major geological and biological events occurred during the Permian Period. Establishing a highresolution stratigraphic and temporal framework is essential to understand their cause-effect relationship. The official International timescale of the Permian System consists of three series(i.e., Cisuralian, Guadalupian and Lopingian in ascending order) and nine stages. In China, the Permian System is composed of three series(Chuanshanian, Yansingian and Lopingian) and eight stages, of which the subdivisions and definitions of the Chuanshanian and Yangsingian series are very different from the Cisuralian and Guadalupian series. The Permian Period spanned ～47 Myr. Its base is defined by the First Appearance Datum(FAD) of the conodont Streptognathodus isolatus at Aidaralash, Kazakhstan with an interpolated absolute age 298.9±0.15 Ma at Usolka, southern Urals, Russia. Its top equals the base of the Triassic System and is defined by the FAD of the conodont Hindeodus parvus at Meishan D section, southeast China with an interpolated absolute age 251.902±0.024 Ma. Thirty-five conodont, 23 fusulinid, 17 radiolarian and 20 ammonoid zones are established for the Permian in China, of which the Guadalupian and Lopingian conodont zones have been served as the standard for international correlation. The Permian δ13 Ccarbtrend indicates that it is characterized by a rapid negative shift of 3–5‰ at the end of the Changhsingian, which can be used for global correlation of the end-Permian mass extinction interval, but δ13 Ccarbrecords from all other intervals may have more or less suffered subsequent diagenetic alteration or represented regional or local signatures only. Permian δ18 Oapatitestudies suggest that an icehouse stage dominated the time interval from the late Carboniferous to Kungurian(late Cisuralian). However, paleoclimate began to ameriolate during the late Kungurian and gradually shifted into a greenhouse-dominated stage during the Guadalupian.The Changhsingian was a relatively cool stage, followed by a globally-recognizable rapid temperature rise of 8–10°C at the very end of the Changhsingian. The87 Sr/86 Sr ratio trend shows that their values at the beginning of the Permian were between 0.70800,then gradually decreased to the late Capitanian minimum 0.70680–0.70690, followed by a persistent increase until the end of the Permian with the value 0.70708. Magenetostratigraphy suggests two distinct stages separated by the Illawarra Reversal in the middle Wordian, of which the lower is the reverse polarity Kiaman Superchron and the upper is the mixed-polarity Illawarra Superchron. The end-Guadalupian(or pre-Lopingian) biological crisis occurred during the late Capitanian, when faunal changeovers of different fossil groups had different paces, but generally experienced a relatively long time from the Jinogondolella altudensis Zone until the earliest Wuchiapingian. The end-Permian mass extinction was a catastrophic event that is best constrained at the Meishan section, which occurred at 251.941±0.037 Ma and persisted no more than 61±48 kyr. After the major pulse at Bed 25, the extinction patterns are displayed differently in different sections. The global end-Guadalupian regression is manifested between the conodont Jinogondolella xuanhanensis and Clarkina dukouensis zones and the endChanghsingian transgression began in the Hindeodus changxingensis-Clarkina zhejiangensis Zone. The Permian Period is also characterized by strong faunal provincialism in general, which resulted in difficulties in inter-continental and inter-regional correlation of both marine and terrestrial systems.
基金supported by the Strategic Priority Research Program of Chinese Academy of Sciences (XDA20020100)the Key Project of National Natural Science Foundation of China (41831177)+1 种基金China Ministry of Science and Technology Project (2018YFB05050000)the 13th Five-year Informatization Plan of Chinese Academy of Sciences (XXH13505-06)
文摘The Serling Co region is located at the transitional zone of the interaction between the Indian monsoon and the westerlies over the Tibetan Plateau. The Serling Co lake covers a water area of2,389 km2(June 2017) in a 45,530 km2drainage basin. Under the dramatic hydro-meteorological changes on the Tibetan Plateau in recent decades, and complex hydrological compositions of rivers and lakes in the basin, the lake area expanded by 43%, from1,667 km2in 1976, to 2,389 km2in 2017 (1)In 2014 it surpassed Nam Co as the largest lake on the Tibetan Plateau [2], and exerts significant effect on regional environmental conditions.
基金This work was supported in part by the Research Grants Council of Hong Kong under Grant GRF 17207818the National Natural Science Foundation of China under Grant 51677160the Themebased Research Scheme(TRS)under T23-701/14-N.
文摘Stability of grid-connected VSCs in DC voltage control(DVC)timescales(i.e.,the frequency range of dynamics covering converter outer controls)has recently caught increased attention,while the existing approaches,such as eigenvalue analysis and dq-domain impedance analysis,have respective limitations on addressing these types of stability issues.This paper proposes an alternative net damping criterion dedicated for analyzing the DVC timescale stability in a multi-VSC system.This criterion is strictly mapped from the Nyquist stability criterion utilizing the gain margin concept,which preserves the advantages of the classical positive net damping criterion suggested by Canay[20]–allowing for decomposition analysis of a subsystem’s contribution to the closed-loop stability in a single-input single-output(SISO)framework,but overcomes its deficiency of possibly erroneous prediction of system dynamic behaviors.Case studies show that the proposed criterion can correctly predict some unstable conditions(e.g.,monotonic divergence)which cannot be identified by the classical net damping criterion.Additionally,the condition for when the classical criterion is available is also pointed out,the proposed criterion can also act as a complement of the classical criterion for stability examination.
基金This work was supported in part by the National Natural Science Foundation of China under Grant No.51977142.
文摘An equivalent source-load MTDC system including DC voltage control units,power control units and interconnected DC lines is considered in this paper,which can be regarded as a generic structure of low-voltage DC microgrids,mediumvoltage DC distribution systems or HVDC transmission systems with a common DC bus.A reduced-order model is proposed with a circuit structure of a resistor,inductor and capacitor in parallel for dynamic stability analysis of the system in DC voltage control timescale.The relationship between control parameters and physical parameters of the equivalent circuit can be found,which provides an intuitive insight into the physical meaning of control parameters.Employing this model,a second-order characteristic equation is further derived to investigate system dynamic stability mechanisms in an analytical approach.As a result,the system oscillation frequency and damping are characterized in a straight forward manner,and the role of electrical and control parameters and different system-level control strategies in system dynamic stability in DC voltage control timescale is defined.The effectiveness of the proposed reduced-order model and the correctness of the theoretical analysis are verified by simulation based on PSCAD/EMTDC and an experiment based on a hardware low-voltage MTDC system platform.
基金supported by the National Natural Science Foundation of China(Grant No.11272359)。
文摘This paper deals with how the purely mathematical approach can be used to solve transient-state instability problems of dissolution-timescale reactive infiltration(DTRI) in fluid-saturated porous rocks. Three key steps involved in such an approach are:(1) to mathematically derive an analytical solution(known as the base solution or conventional solution) for a quasi-steady state problem of the dissolution timescale, which is viewed as a frozen state of the original transient-state instability problem;(2)to mathematically deduce a group of first-order perturbation partial-differential equations(PDEs) for the quasi-steady state problem;(3) to mathematically derive an analytical solution(known as the perturbation solution or unconventional solution) for this group of first-order perturbation PDEs. Because of difficulty in mathematically solving a transient-state instability problem of DTRI in general cases, only a special case, in which some nonlinear coupling between governing PDEs of the problem can be decoupled, is considered to illustrate these three key steps in this study. The related theoretical results demonstrated that the transient chemical dissolution front can become unstable in the DTRI system of large Zh numbers when the long wavelength perturbations are applied to the system. This new finding may lay the theoretical foundation for developing innovative technique to exploit shale gas resources in the deep Earth.
基金supported by the National Natural Science Foundation of China(Grant Nos. 10825520,11105088,11175230 and 11290164)Shanghai Supercomputer Center and Supercomputing Center of Chinese Academy of Sciences
文摘Using molecular dynamics simulations, we show that free diffusion of a nanoscale particle (molecule) with asymmetric structure critically depends on the orientation in a finite timescale of picoseconds to nanoseconds. In a timescale of ~100 ps, there are ~10% more possibilities for the particle moving along the initial orientation than moving opposite to the orientation; and the diffusion distances of the particle reach ~1 nm. We find that the key to this observation is the orientation-dependence of the damping force to the moving of the nanoscale particle and a finite time is required to regulate the particle orientation. This finding extends the work of Einstein to nano-world beyond random Brownian motion, thus will have a critical role in the understanding of the nanoscale world.
