Long-time Range Research Articles

High-precision temperature control of helium Joule–Thomson cryocooler: Long-term temperature stability

To meet the refrigeration requirements of scientific instruments for mK-level temperature stability over a long-time range in the liquid helium temperature, the temperature characteristics and high-precision control strategies of the helium Joule-Thomson cryocooler (JTC) have been experimentally investigated for the first time. Based on the Ideal Gas Law, the influencing mechanism of pre-cooling temperature, gas reservoir volume, and liquid phase volume fraction on refrigeration temperature were qualitatively analyzed and experimentally verified. An active control studies of pre-cooling temperature, low-pressure and heat load were carried out to verify the feasibility of active temperature control of helium JTC. Finally, a long-term temperature stability of ±1 mK/h was successfully achieved when a multi-stage active control strategy was adopted, which is the optimal long-term temperature stability of helium JTC that have been reported to date.

Antipersistent energy-current correlations in strong long-ranged Fermi-Pasta-Ulam-Tsingou-type models.

We study heat transfer in one-dimensional Fermi-Pasta-Ulam-Tsingou-type systems with long-range (LR) interactions. The strength of the LR interaction between two lattice sites decays as a power σ of the inverse of their distance. We focus on the strong LR regime (0≤σ≤1) and show that the thermal transport behaviors are remarkably nuanced. Specifically, we observe that the antipersistent (negative) energy current correlation in this regime is intricately dependent on σ, displaying a nonmonotonic variation. Notably, a significant qualitative change occurs at σ_{c}=0.5, where with respect to other σ values the correlation shows a minimum negative value. Furthermore, our findings also demonstrate that within the long-time range considered, these antipersistent correlations will eventually vanish for certain σ>0.5. The underlying mechanisms behind these intriguing phenomena are related to the crossover of two diverse space-time scaling properties of equilibrium heat correlations and the various scattering processes of phonons and discrete breathers.

Nonlinear dynamics of time-varying curvature balance rope coupled with time-varying length hoisting rope in friction hoisting system

Mine friction hoisting system is a typical multi-body system composed of traction sheave, conveyance, hoisting rope, and balance rope. Hoisting rope is of large-scale and flexible tension, leading to large amplitude elastic vibration and huge tension fluctuation during hoisting movement. Balance rope is of small tension amplitude and bending modulus, undergoing significant curvature changes, large displacement, and large deformation. Considering the complex coupling vibrations between the moving hoisting rope and balance rope in the ultra-kilometer-deep shaft, a coupling modeling method of the variable-length hoisting rope with the variable-curvature balance rope is proposed. Based on the absolute nodal coordinate formulation(ANCF), the balance rope is modeled by non-equal-length and variable-number elements, and the hoisting ropes on both sides are modeled by variable-length and variable-number elements. A flexible rope vibration experiment platform is built in the laboratory to verify correctness of the proposed theoretical model.The experimental results are in good agreement with those in theoretical simulation. Besides, the nonlinear coupling dynamic behaviors of hoisting rope and balance rope in an ultra-kilometer-deep well are studied. It reveals the non-stationary phenomenon of hoisting rope and balance rope with a long-time range. Both sides of flat balance rope undergo large bending deformation and non-stationary response when transient resonance occurs in hoisting ropes.

Magnesiation roasting kinetics exploration of vanadium slag toward minimization of tailing toxicity

In order to minimize the toxicity of vanadium extraction tailings, the vanadium extraction efficiency should be as high as possible to minimize the residual V(V) content in tailings. In this work, the kinetics of the novel magnesiation roasting of vanadium slag, including the roasting mechanism and kinetic models, is explored to intensify the vanadium extraction. By combination of various characterizations, the microscopic mechanism of magnesiation roasting is revealed, which indicates the simultaneous occurrence of the salt-formation→oxidation routine (major) and the oxidation→salt-formation routine (minor). Macroscopic kinetic model studies show the magnesiation roasting of vanadium slag proceeds in two stages. In the initial 50 min, the roasting follows the Interface Controlled Reaction Model, during which the stable roasting temperature is essential to intensify the magnesiation. In the long-time range (50–90 min), the roasting follows the Ginstling-Brounstein Model, during which the acceleration of air blow rate is most favorable. With intensified roasting kinetics, the vanadium extraction efficiency is as high as 96.65%. This work has provided the guideline to intensify the magnesiation roasting of vanadium slag for vanadium extraction, which can not only minimize the tailing toxicity of vanadium extraction but also accelerate the industrial application of the novel magnesiation roasting technique.

Size-controllable colloidal Ag nano-aggregates with long-time SERS detection window for on-line high-throughput detection

Making metal nanoparticle aggregates is a common way to improve surface-enhanced Raman scattering (SERS) enhancement via the formation of hot spots between nanoparticles. Here, we propose a “freeze-thaw-ultrasonication” method to obtain stable colloidal Ag nano-aggregates (AgNAs) with controllable sizes, which can remain stable for a few days. Compared with other method using aggregation reagents (e.g., organic molecules and salt), this method can maintain metal surface charges and adsorption affinity, which ensures the excellent SERS stability and sensitivity. The SERS detection window during the experiment can reach more than 25 min, which makes it a prerequisite for accurate SERS detection during a long-time range. Combining the obtained stable AgNAs with microfluidic devices, we established a sequential SERS on-line continuous detection method for the high-throughput detection of multiplex samples. The UV-Fenton degradation process of methylene blue (MB) is continuously on-line monitored through this platform, which is more sensitive than the UV–Vis Spectrum. Moreover, we have realized the sensitive and accurate detection of 5-nitro-8-hydroxyquinoline (5-NQ) with antibacterial and anticancer activities based on chloride-functionalized silver, which paved a way for SERS high-throughput analysis in bioanalysis and other fields.

Transformer Based Water Level Prediction in Poyang Lake, China

Water level is an important indicator of lake hydrology characteristics, and its fluctuation significantly affects lake ecosystems. In recent years, deep learning models have shown their superiority in the long-time range prediction of hydrology processes, while the application of deep learning models with the attention mechanism for lake water level prediction is very rare. In this paper, taking Poyang Lake as a case study, the transformer neural network model is applied to examine the model performance in lake water level prediction, to explore the effects of the Yangtze River on lake water level fluctuations, and to analyze the influence of hyper-parameters (window size and model layers) and lead time on the model accuracy. The result indicated that the transformer model performs well in simulating the lake water level variations and can reflect the temporal water level variation characteristics in Poyang Lake. In the testing stage, the RMSE values were recorded in the range of 0.26–0.70 m, and the NSE values are higher than 0.94. Moreover, the Yangtze River inflow has a great influence on the lake water level fluctuation of Poyang Lake, especially in flood and receding periods. The contribution rate of the Yangtze River in RMSE and NSE is higher than 80% and 270%, respectively. Additionally, hyper-parameters, such as window size and model layers, significantly influence the transformer model simulation accuracy. In this study, a window size of 90 d and a model layer of 6 are the most suitable hyper-parameters for water level prediction in Poyang Lake. Additionally, lead time may affect the model accuracy in lake water level prediction. With the lead time varied from one to seven days, the model accuracy was high and RMSE values were in the range of 0.46–0.73 m, while the RMSE value increased to 1.37 m and 1.82 m with the lead time of 15 and 30 days, respectively. The transformer neural network model constructed in this paper was the first to be applied to lake water forecasting and showed high efficiency in Poyang Lake. However, few studies have tried to use transformer model coupling with the attention mechanism for forecasting hydrological processes. It is suggested that the model can be used for long sequence time-series forecasting in hydrological processes in other lakes to test its performance, providing further scientific evidence for the control of lake floods and management of lake resources.

A dataset of ultraviolet radiation reconstruction in China during 2015–2020

Ultraviolet radiation data can provide data support for many fields such as agriculture, ecology, environmental science, materials science, and human health. They have important application value in ecosystem succession, climate change research and environmental impact assessment. But with so little observational data and a short time scale, obtaining accurate, long-time, and wide range UV radiation data will provide scientific data support for relevant research. Therefore, based on the observation data of existing stations, in this paper, we constructed a method suitable for the reconstruction of ultraviolet radiation at the national scale, and combined with the conventional meteorological data observed for a long time, so as to obtain a dataset of ultraviolet radiation reconstruction. During the production of this dataset, first, we got the historical data of total surface radiation in accordance with the "hybrid model". Then, we created the UV radiation estimation formula by using clear sky index and other parameters. Finally, we calculated the reconstructed UV radiation data of 705 observation stations in China followed by the process of accuracy verification. The time range of this dataset is during 2015–2020.

A Comprehensive Societal Energy Return on Investment Study of Portugal Reveals a Low but Stable Value

Energy return on investment (EROI) is a ratio of the energy obtained in relation to the energy used to extract/produce it. The EROI of fossil fuels is globally decreasing. What do the declining EROIs of energy sources imply for society as a whole? We answer this question by proposing a novel EROI measure that describes, through one parameter, the efficiency of a society in managing energy resources over time. Our comprehensive societal EROI measure was developed by (1) expanding the boundaries of the analysis up to the useful stage; (2) estimating the amount of energy embodied in the energy-converting capital; (3) considering non-conventional sources such as the muscle work of humans and draught animals; and (4) considering the influence of imported and exported energy. We computed the new EROI for Portugal as a case study. We find a considerably lower EROI value, at around 3, compared to those currently available, which is stable over a long-time range (1960–2014). This suggests an independence of EROI from economic growth. When estimated at the final stage, using conventional methods (i.e., without applying the four novelties here introduced), we find a declining societal EROI. Therefore, our results imply that the production of new and more efficient final-to-useful energy converting capital has historically kept societal EROI around a stable value by offsetting the effects of the changing returns of energy sources at the primary and final stages. This will be crucial in the successful transition to renewables.

Temporal Shape-Based Fusion Method to Generate Continuous Vegetation Index at Fine Spatial Resolution

In this study, a temporal shape–based fusion method using a spatially and temporally moving window is proposed to incorporate time lag of fine and coarse resolution observations, and to fully utilize target fine resolution pixel and similar coarse resolution pixels in the process. This method provides high accuracy fused images with Pearson’s r of ~0.95, root mean square error of ~0.04, and bias of ~0.01 for commonly used fine spatial resolution satellites, including Landsat 7 and 8, Sentinel 2, and Gaofen 1, over different heterogeneous regions, such as urban, mountain, forest, and savanna regions. The fused fine resolution Enhanced Vegetation Index (EVI) time series using different fine spatial resolution satellites data as input are all highly correlated with the PhenoCam monitored green chromatic coordinate, with no temporal lag. Compared with commonly used data fusion method, this method provides equivalent and slightly higher accuracy because both neighboring similar pixels and the annual temporal variation are fully considered. This temporal shape–based fusion method does not require each input fine resolution image to be cloud-free; therefore, it can be used at a large spatial scale without further preprocessing and generates continuous datasets over a long-time range with only one input preparation process. The factors that could affect the method accuracy are the cloud detection accuracy of fine resolution data and the temporal continuity of the coarse resolution data. The method may also be used to produce spatially and temporally continuous surface reflectance and other surface reflectance derived indices.

Structural analysis and mechanical properties of thermal battery by flexible phase change materials [P.C.M.

An ancient B.T.M. with P.C.M. was controlled through the issues of high inflexibility of phase change material, leakage problems and very low conductivity in thermal energy. This research paper reports a facile batter thermal management and creativity along with induced non-rigid phase change material composites. This battery model can be determined by the flexible phase change material composites along with an intervention due to the recovery in shape and non-rigidity of flexible phase change components. This assemble was modelled to be efficient and compact without any requirement for grease. A constant state reveals various stages of phase change material which has various properties in thermal efficiency. A unified state was linked with the recovery shape of flexible phase change components, which can cause a low resistance in FCPCM and battery. Battery thermal management demonstrates the perfect process of thermal control power. If the battery was discharged from 90 to 10% of charge, then the temperature of flexible phase change components depends upon battery thermal management. It was 44.5 °C during the 3.5 °C rate, which was 29.8 °C lower than no phase change material. It also reveals low-temperature oscillation inside the long-time process and range of heat of recovered phase change material. The performance of battery thermal management and its flexibility will give perceptions of passive battery thermal management systems.

Structural Analysis and Mechanical Properties of Thermal Battery by Flexible PCM

An ancient BTM with PCM was controlled through the issues of high inflexibility of phase change material, leakage problems and very low conductivity in thermal energy. This research paper reports a facile batter thermal management and creativity along with induced non-rigid phase change material composites. This battery model can be determined by the flexible phase change material composites along with an intervention due to the recovery in shape and non-rigidity of flexible phase change components. This assemble was modeled to be efficient and compact without any requirement for grease. A constant state reveals various stages of phase change material which has various properties in thermal efficiency. A unified state was linked with the recovery shape of flexible phase change components which can cause a low resistance in FCPCM and battery. Battery thermal management demonstrates the perfect process of thermal control power. If the battery was discharged from 90 to 10% of charge, then the temperature of flexible phase change components depends upon battery thermal management. It was 44.5°C during the 3.5°C rate which was 29.8°C lower than no phase change material. It also reveals low-temperature oscillation inside the long-time process and range of heat of recovered phase change material. The performance of battery thermal management and its flexibility will give perceptions of passive battery thermal management systems.

Recommendation System With Hierarchical Recurrent Neural Network for Long-Term Time Series

Nowadays, recommendation systems are widely used on various services. This system predicts what item a user will use next using large amounts of stored user history. Recommendation systems are commonly applied in various fields as movies, e-commerce, and social services. However, previous researches on recommendation systems commonly overlooked the importance of item usage sequence and time intervals of the time series data from users. We provide a novel recommendation system that incorporates these temporal properties of the user history. We design a recurrent neural network (RNN) model with a hierarchical structure so that the sequence and time intervals of the user’s item usage history can be considered. The model is divided into two layers: a layer for a long time and a layer for a short time. We conduct experiments on real-world data such as Movielens and Steam datasets, which has a long-time range, and show that our new model outperforms the previous widely used recommendation methods, including RNN-based models. We also conduct experiments to find out the influence of the length and time interval of sequences in our model. These experimental results show that both sequence length and time interval are influential, indicating that it is important to consider the temporal properties for long-term sequences.

Hypocoercivity without confinement

Hypocoercivity methods are applied to linear kinetic equations with mass conservation and without confinement in order to prove that the solutions have an algebraic decay rate in the long-time range, which the same as the rate of the heat equation. Two alternative approaches are developed: an analysis based on decoupled Fourier modes and a direct approach where, instead of the Poincare inequality for the Dirichlet form, Nash’s inequality is employed. The first approach is also used to provide a simple proof of exponential decay to equilibrium on the flat torus. The results are obtained on a space with exponential weights and then extended to larger function spaces by a factorization method. The optimality of the rates is discussed. Algebraic rates of decay on the whole space are improved when the initial datum has moment cancellations.

La invención del Enemigo (Las figuras diabólicas en el Valle del Ebro, del siglo IV al XVII)

Este trabajo intenta trazar la historia del diablo desde el inicio del cristianismo hasta el siglo XVII en una región delimitada, correspondiente más o menos a la actual provincia de La Rioja. Sustitúyese cualquier concepto previo de «diablo» por las representaciones concretas que pueden reconocerse en los documentos. En lugar de una figura estable, heredera de tradiciones pre-romanas o pre-cristianas, se revela así un personaje que evoluciona de un simple espíritu invasor a rey infernal o perturbador del alma. Las figuras de más peso del panteón católico -la Virgen y los santos- se elaboran y difunden a su sombra. El diablo ocupa por un buen tiempo el centro efectivo de la doctrina cristiana, y juega un gran papel en la creación del espacio psicológico interior.

Divergent memories and visions of the future in conflicts over mining development

Conflicts over extractive development often center around predicting future profits and economic growth, and estimating industrial pollution. How these projections are understood and seen as legitimate and trustworthy depends on social actors' environmental imaginaries and timescapes. Thus, I examine the temporal and cultural dynamics of natural resource politics, particularly how affective connections to the past and future mobilize support and opposition to new mining. I use the case of proposed copper mines in the rural Minnesota Iron Range region to explore the different environmental imaginaries and timescapes that mining opponents and proponents use to understand the potential socio-environmental impacts, and to legitimate their positions. Proponents, including long-time and working class Iron Range residents and mining corporations, view the region as an industrial landscape built by mining and hope new proposals will renew the past to create a prosperous future. Meanwhile, environmental groups who oppose mining view the region through an environmental imaginary based on outdoor recreation, and draw on collective memories of family and youth trips to understand new extractive projects as a rupture to their vision of the future. I show that resource extraction is understood through temporalities that differ across intersections of class and region, and that emotional meanings of the past and visions of the future animate contemporary political action.Keywords: Resource extraction, mining, environmental imaginaries, timescapes, collective memory, environmental politics, emotions

Joint Detection and Localization of Vessels at Sea With a GNSS-Based Multistatic Radar

This paper addresses the exploitation of global navigation satellite systems as opportunistic sources for the joint detection and localization of vessels at sea in a passive multistatic radar system. A single receiver mounted on a proper platform (e.g., a moored buoy) can collect the signals emitted by multiple navigation satellites and reflected from ship targets of interest. This paper puts forward a single-stage approach to jointly detect and localize the ship targets by making use of long integration times (tens of seconds) and properly exploiting the spatial diversity offered by such a configuration. A proper strategy is defined to form a long-time and multistatic range and Doppler (RD) map, where the total target power can be reinforced with respect to, in turn, the case in which the RD map is obtained over a short dwell and the case in which a single transmitter is employed. The exploitation of both the long integration time and the multiple transmitters can greatly enhance the performance of the system, allowing counteracting the low-power budget provided by the considered sources representing the main bottleneck of this technology. Moreover, the proposed single-stage approach can reach superior detection performance than a conventional two-stage process where peripheral decisions are taken at each bistatic link and subsequently the localization is achieved by multilateration methods. Theoretical and simulated performance analysis is proposed and also validated by means of experimental results considering Galileo transmitters and different types of targets of opportunity in different scenarios. Obtained results prove the effectiveness of the proposed method to provide detection and localization of ship targets of interest.

Initial-Boundary Value Problem for Stimulated Raman Scattering Model: Solvability of Whitham Type System of Equations Arising in Long-Time Asymptotic Analysis

An initial-boundary value problem for a model of stimulated Raman scattering was considered in [Moskovchenko E.A., Kotlyarov V.P., J. Phys. A: Math. Theor. 43 (2010), 055205, 31 pages]. The authors showed that in the long-time range $t\to+\infty$ the $x>0$, $t>0$ quarter plane is divided into 3 regions with qualitatively different asymptotic behavior of the solution: a region of a finite amplitude plane wave, a modulated elliptic wave region and a vanishing dispersive wave region. The asymptotics in the modulated elliptic region was studied under an implicit assumption of the solvability of the corresponding Whitham type equations. Here we establish the existence of these parameters, and thus justify the results by Moskovchenko and Kotlyarov.

In Russian

For the first time, it is demonstrated that the methanol diffusion in the H-ZSM-5/Al 2 O 3 catalyst pellet is anomalous and is described by the time-fractional diffusion equation. The regime of the methanol transport is sub-diffusive. The aim of the present work is a description of the experimental data of the methanol transport through the pellet of the zeolite-containing catalyst for olefins synthesis form the methanol based on the solutions of the diffusion equation of the second Fick’s law of diffusion and the time-fractional diffusion equation. In this work, the mesoporous catalyst based on zeolite H-ZSM-5 and alumina with zeolite/alumina ratio 3/1 by mass is used. The methanol transport has been studied using the developed method of mass transfer process investigation in the porous solid media in flow regime. The method is based on the porous sample saturation by a pulse of the adsorbate. The porous sample is installed to the diffusion cell. Adsorbate quantity evolution versus time is chromatographically analyzed. The porous sample is installed to the diffusion cell so that half of its surface is impermeable for adsorbate which allows applying the von Neumann boundary conditions to sole the diffusion equation. The investigation resulted in the obtaining the relative concentration decay versus time on the boundary of the catalyst pellet. The obtained experimental dependences are analyzed on the whole temporal scale using the analytic solution of the diffusion equation based on the second Fick’s law of diffusion. However, the correspondence between the theoretical solution and the experimental data is very poor. The asymptotic analysis of the experimental data in the long-time range linearized in the logarithmic coordinates according to the solution of the standard diffusion equation has demonstrated that the equation for the second Fick’s law of diffusion is inapplicable to a description of the obtained experimental data because the slope of the experimental data is far from the theoretical one which is equal to unity. On the other, an hand analysis of the experimental data in the long-time range linearized in the logarithmic coordinates according to the solution of the time-fractional diffusion equation revealed the high correlation between the theoretical solution and the experimental data. The calculated values of the fractional order and the fractional diffusion coefficient are independent on the experimental conditions. This means that these characteristics are individual for each pair of the porous media and diffusate and may be associated with the methanol adsorption on the active sites on the surface of the catalyst. The fractional order value is lower than unity, which reveals the presence of the sub-diffusive regime of transport, which is slower comparing to the standard diffusion. Based on the analysis of the methanol mass transfer in the pellet of the zeolite-containing catalyst, it is found that the solution of the time-fractional diffusion equation gives good fit to the experimental data comparing to the solution of the standard diffusion equation. The values of the diffusion coefficients and the fractional orders calculated on the long times are equal to the values estimated for the whole temporal range. It is found that the methanol transfer in the catalyst pellet occurs in the slow sub-diffusive regime. The experimental evidence of the presence of an anomalous diffusion is fundamental for the theoretical understanding the mass transfer process and modeling as well as for application during solving the engineering problems.

Foreign Exchange Market Contagion in Central Europe from the Viewpoint of Extreme Value Theory

This paper examines contagion in the foreign exchange markets of three Central European countries and the euro area. Contagion is viewed as the occurrence of extreme events taking place in different countries simultaneously and is assessed with a measure of asymptotic tail dependence among the studied distributions. Currency crisis contagion is one strand of this research. However, the main aim of the paper is to examine the potential of bubble contagion. To this end the representative exchange rates are linked to their fundamentals using a cointegration approach. Given the long-time range required by cointegration testing, the variables are first tested for unit roots with structural breaks, whose existence is supported by these tests. In the sequel, the extreme values of the differences between actual daily exchange rates and their monthly equilibrium values determine the episodes associated with large departures from equilibrium. Using tools from Extreme Value Theory, we analyse the transmission of both standard crisis and bubble formation events in the examined currency markets. The results reveal a significant potential for contagion in the currency markets of Central Europe.

Simultaneous Analysis of Equilibrium Fluctuations at the Surface and in the Bulk of a Binary Liquid Mixture by Dynamic Light Scattering.

For the first time, we demonstrate that it is possible to simultaneously analyze microscopic fluctuations at the surface and in the bulk of a binary liquid mixture by dynamic light scattering in macroscopic thermodynamic equilibrium. For a model system containing n-octacosane and ethanol, three individual signals distinguishable in the time-resolved analysis of the scattered light intensity appear on different time scales. One oscillatory signal from surface fluctuations at the vapor-liquid interface in the short-time range and two exponential Rayleigh signals from fluctuations in temperature and concentration in the bulk of fluid in the long-time range could be associated with hydrodynamic modes. This microscopic information allows for a simultaneous determination of the macroscopic properties interfacial tension, kinematic viscosity, thermal diffusivity, and mutual diffusivity within a single experimental run. The presented approach represents a worthwhile strategy, for example, in the context of sensor development for an effective multiproperty determination of fluid systems.